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000
FXUS66 KPQR 182351
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
350 PM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL INCREASE TONIGHT AS A MORE ORGANIZED FRONTAL
SYSTEM PUSHES ONSHORE. A COLDER UPPER TROUGH MOVES ACROSS THE AREA
FRIDAY...WHICH WILL LOWER SNOW LEVELS BELOW THE CASCADE PASSES. MILD
AND VERY WET WEATHER IS EXPECTED THIS WEEKEND WITH AN ATMOSPHERIC
RIVER BRINGING HEAVY RAIN TO THE REGION. THE EXACT LOCATION OF THE
JET STREAM AND ASSOCIATED MOISTURE PLUME IS STILL IN QUESTION...BUT
THERE IS INCREASING CONFIDENCE THAT IT WILL TAKE AIM AT SW WASHINGTON
AND NW OREGON. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM....TONIGHT THROUGH SUNDAY...NWS DOPPLER RADAR CONTINUES
TO DEPICT LIGHT RAIN SPREADING ACROSS THE REGION THIS AFTERNOON IN
ASSOCIATION WITH AN APPROACHING FRONTAL SYSTEM. RAINFALL TOTALS THIS
AFTERNOON HAVE BEEN LIGHT...WITH TOTALS GENERALLY AROUND ONE TENTH OF
AN INCH FOR MOST SPOTS. SOME OF THE HIGHER ELEVATION LOCATIONS HAVE
MEASURED AROUND ONE QUARTER INCH. MODELS REMAIN IN AGREEMENT THAT THE
FRONTAL BOUNDARY WILL PUSH ONSHORE THIS EVENING. AHEAD OF THE
FRONT...GUSTY SOUTH WINDS WILL INCREASE ACROSS THE COASTAL
AREAS...WITH GUSTS INTO THE 50-55 MPH RANGE THIS EVENING FOR THE MORE
EXPOSED BEACHES AND HEADLANDS.

THE SYSTEM TONIGHT WILL BRING A SHOT OF RAIN TONIGHT THROUGH EARLY
FRIDAY WITH AROUND AN INCH OF RAIN FOR THE COAST AND COAST
RANGE AND AROUND A HALF INCH FOR THE VALLEY. SNOW LEVELS WILL
GRADUALLY RISE A LITTLE THIS EVENING AHEAD OF THE FRONT...BUT LOWER
DOWN TO BELOW THE CASCADE PASSES BY EARLY FRIDAY MORNING AS THE COLD
UPPER TROUGH SLIDES OVER THE REGION. HOWEVER...THE BULK OF THE
PRECIPITATION WILL HAVE FINISHED BY THE TIME SNOW LEVELS COME DOWN.
OVERALL...A FEW INCHES OF SNOW AT THE PASSES ARE POSSIBLE WITH A FEW
ADDITIONAL INCHES OF SNOW AT THE HIGHER CASCADE ELEVATIONS. ADDED A
SLIGHT CHANCE OF THUNDERSTORMS TO THE FORECAST FOR THE COAST RANGE
AND POINTS WEST FOR EARLY TOMORROW MORNING. THE UPPER TROUGH MOVES
THROUGH THE AREA AND MODEL FORECAST SOUNDINGS INDICATE DECENT
INSTABILITY.

MODELS CONTINUE TO REMAIN IN GOOD AGREEMENT THAT A VERY MOIST
ATMOSPHERIC RIVER PATTERN WILL SET UP DIRECTING LARGE AMOUNTS OF
MOSITURE AT SW WASHINGTON AND NW OREGON THIS WEEKEND. HEAVY RAINFALL
LIKELY BEGINS BY EARLY SATURDAY MORNING AND CONTINUES THROUGH AT
LEAST SUNDAY. THE COAST RANGE...WILLAPA HILLS...CASCADES...AND
FOOTHILLS WILL LIKELY SEE ON THE ORDER OF 8 TO 12 INCHES OF RAINFALL.
LOCATIONS ON THE COAST MAY SEE 5 TO 7 INCHES OF RAIN...WHILE THE
INTERIOR VALLEY LOCATIONS CAN EXPECT 3 TO 4 INCHES. WHILE SOME
UNCERTAINTY IN THE PRECISE AREAS OF MAXIMUM RAINFALL
EXISTS...CONFIDENCE IS INCREASING THAT LARGE AMOUNTS OF PRECIPITATION
WILL OCCUR ACROSS THE FORECAST AREA WITH THIS SYSTEM. AS A
RESULT...THERE IS THE POTENTIAL FOR SHARP RISES ON AREA RIVERS AND
STREAMS THAT MAY RESULT IN FLOODING. SEE THE HYDROLOGY SECTION FOR
MORE DETAILS.

IN ADDITION...THOSE PLANNING TO BE ALONG THE COAST AT AREAS BEACHES
SHOULD CLOSELY MONITOR THE CONDITIONS FOR THIS WEEKEND. RAPIDLY
BUILDING SEAS WILL BRING THE POTENTIAL FOR DANGEROUS HIGH SURF ALONG
THE AREA BEACHES ON FRIDAY. LONG PERIOD SWELLS MAY REACH SHORE AND
SURPRISE INDIVIDUALS WHO ARE UNAWARE. ANYONE ON THE BEACHES SHOULD
EXERCISE EXTREME CAUTION AND AVOID THE SURF ZONE AS LARGE WAVES MAY
WASH OVER BEACHES AND JETTIES WITH LITTLE WARNING. SOME POTENTIAL FOR
MINOR TIDAL OVERFLOW IS POSSIBLE FOR SATURDAY AND SUNDAY...ESPECIALLY
AROUND HIGH TIDES. THIS THREAT COULD BE ENHANCED BY HIGH FLOWS ON
RIVERS IN RESPONSE TO THE RAINFALL THIS WEEKEND.  CULLEN

&&

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...MODELS AGREE THE
WEEKEND RAIN/FLOODING EVENT WILL WIND DOWN SUNDAY NIGHT INTO MONDAY.
A MUCH WEAKER FRONT MAY SLIDE SOUTHWARD ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON MONDAY NIGHT INTO TUESDAY. MODELS HAVE WAVERED
A BIT ON THIS SYSTEM SO POPS WERE GENERALLY KEPT IN THE HIGH END
CHANCE TO LOW END LIKELY. CONDITIONS SHOULD TEMPORARILY DRY OUT LATE
TUESDAY BEFORE A COLDER STORM SYSTEM BRINGS SHOWERS TO THE AREA ON
WEDNESDAY...BUT DISCREPANCIES CONTINUE AMONG THE MODELS. SNOW LEVELS
WILL LIKELY LOWER WELL BELOW PASS LEVEL SO HOLIDAY TRAVELERS HEADED
OVER THE CASCADE PASSES WILL CERTAINLY NEED TO MONITOR THE FORECAST.
COLD NORTHERLY WILL FOLLOW AND ALLOW TEMPERATURES TO COOL WELL BELOW
NORMAL AS CONDITIONS DRY OUT LATE WEEK. EASTERLY WINDS WILL LIKELY
RETURN. /NEUMAN

&&

.HYDROLOGY...SITUATION SETTING UP FOR A MEMORABLE HYDROLOGIC EVENT
MAINLY FOR LATER THIS WEEKEND AND HEADING INTO NEXT WEEK. STRONG AND
DEEP MOIST WESTERLY FLOW WILL BEGIN CROSSING THE PACNW COAST COME
SATURDAY MORNING. A VERY LONG FETCH OF MOISTURE IS STRETCHING ACROSS
THE PACIFIC WITH ORIGINS WEST TO THE SOUTH CHINA SEA. THIS MOIST AIR
MASS WILL BE PUSHED EAST BY A 150 TO 170 KT JET AND WESTERLY 25 TO
50 KT LOWER LEVEL WINDS. AS SUCH...THIS CONTINUES TO GIVE THE
APPEARANCE OF A CLASSIC HIGH PRECIPITATION ATMOSPHERIC RIVER EVENT
WHERE THE DEEP MOIST FLOW WILL SPEND A SIGNIFICANT AMOUNT OF TIME
ON A NEARLY PERPENDICULAR COURSE AGAINST THE COAST RANGE WITH THE
CASCADES TAKING A BIT HIGHER OF THE IMPACT. AS OF THE MORNING MODEL
RUNS AND RECENT NWRFC UPDATES...IT APPEARS MULTIPLE COAST RANGE
RIVERS HAVE A MODERATE POTENTIAL OF EXCEEDING FLOOD STAGE.
ADDITIONALLY...THIS EVENT HAS SUFFICIENT DEPTH TO BRING SIGNIFICANT
RAINS TO THE NORTH OREGON AND SOUTH WASHINGTON CASCADES WHERE RIVERS
WILL ALSO SEE POTENTIAL FOR NOTABLE FLOODING. WILL CONTINUE THE
HYDROLOGIC OUTLOOK (PDXESFPQR) PRODUCT HIGHLIGHTING CONCERNS. KEEP
IN MIND THAT DETAILS WILL ALWAYS BE IN FLUX UNDER THESE SCENARIOS AS
SUBTLE NORTH/SOUTH SHIFTS COLD MAKE DRAMATIC DIFFERENCES IN WHICH
BASINS RECEIVE EXTENDED PERIODS OF MODERATE TO HEAVY RAIN. PLEASE
CONTINUE TO FOLLOW THE LATEST FORECASTS AND IMPACTS AS CONDITIONS
WARRANT. RIVER FORECASTS ARE AVAILABLE ON OUR WEB PAGE AT:
HTTP://WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR (ALL LOWER CASE)

/JBONK

&&

.AVIATION...MIX OF VFR AND MVFR CIGS AND VIS THIS EVENING WILL
DROP TO MVFR/IFR AFTER MIDNIGHT. POST FRONTAL SHOWERS ACROSS THE
AREA WILL BRING DOWN CIGS AND VIS. WINDS AT KTTD GUSTING TO 30 KTS
WILL HELP KEEP CIGS UP AT KTTD AND POSSIBLY KPDX...THOUGH CIGS MAY
DROP TO MVFR/IFR WITH HEAVIER SHOWERS. RAIN TO CONTINUE THROUGH
THE DAY FRIDAY...WITH A CHANCE OF THUNDERSTORMS ALONG THE COAST
FRIDAY MORNING. CIGS AND VIS LIKELY TO IMPROVE TO A MIX OF VFR AND
MVFR BY FRIDAY AFTERNOON.

PDX AND APPROACHES...VFR CIGS LIKELY TO STAY VFR THIS
EVENING...WITH PERIODS OF MVFR CIGS AND VIS STARTING LATE THIS
EVENING BEHIND THE COLD FRONT. CIGS AND VIS LIKELY TO DROP TO
MVFR/IFR EARLY FRIDAY MORNING...BUT IMPROVE TO VFR BY FRIDAY
AFTERNOON. -MCCOY

&&

.MARINE...COMBINED SEAS AROUND 12 FT BUILDING TO 14 TO 16 FT BY
FRIDAY MORNING. SEAS WILL RAPIDLY BUILD DURING THE AFTERNOON HOURS AS
THE 20 TO 22 FT SWELL APPROACHES...BRINGING SEAS UP TO 22 FT BY
FRIDAY EVENING. SEAS WILL REMAIN AROUND 20 TO 22 FT THROUGH
SATURDAY MORNING. AS THE SWELL BEGINS TO DROP OFF...SOUTHERLY
WINDS INCREASE AHEAD OF OUR NEXT STRONG COLD FRONT. GALES LOOK
LIKELY WITH THIS SYSTEM...KEEPING SEAS AROUND 20 TO 22 FT THROUGH
SATURDAY MORNING. SEAS BEGIN TO DROP BELOW 20 FT SATURDAY
AFTERNOON BEHIND THE FRONT...AS WINDS EASE...BUT SEAS WILL STAY IN
THE UPPER TEENS THROUGH SUNDAY EVENING.

ANOTHER WEAK FRONTAL SYSTEM COULD KEEP SMALL CRAFT WINDS ACROSS
OUR SOUTHERN WATERS THROUGH SUNDAY NIGHT. OTHERWISE...RELATIVELY
BENIGN WEATHER EXPECTED EARLY NEXT WEEK AS HIGH PRESSURE BUILDS
OVER THE WATERS. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 10 AM FRIDAY TO 4 AM PST SATURDAY FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...HIGH SURF ADVISORY FROM 10 AM FRIDAY TO 4 AM PST SATURDAY FOR
     SOUTH WASHINGTON COAST.

PZ...GALE WARNING UNTIL MIDNIGHT PST TONIGHT FOR COASTAL WATERS FROM
     CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 3 PM PST
     SUNDAY.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 182351
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
350 PM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL INCREASE TONIGHT AS A MORE ORGANIZED FRONTAL
SYSTEM PUSHES ONSHORE. A COLDER UPPER TROUGH MOVES ACROSS THE AREA
FRIDAY...WHICH WILL LOWER SNOW LEVELS BELOW THE CASCADE PASSES. MILD
AND VERY WET WEATHER IS EXPECTED THIS WEEKEND WITH AN ATMOSPHERIC
RIVER BRINGING HEAVY RAIN TO THE REGION. THE EXACT LOCATION OF THE
JET STREAM AND ASSOCIATED MOISTURE PLUME IS STILL IN QUESTION...BUT
THERE IS INCREASING CONFIDENCE THAT IT WILL TAKE AIM AT SW WASHINGTON
AND NW OREGON. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM....TONIGHT THROUGH SUNDAY...NWS DOPPLER RADAR CONTINUES
TO DEPICT LIGHT RAIN SPREADING ACROSS THE REGION THIS AFTERNOON IN
ASSOCIATION WITH AN APPROACHING FRONTAL SYSTEM. RAINFALL TOTALS THIS
AFTERNOON HAVE BEEN LIGHT...WITH TOTALS GENERALLY AROUND ONE TENTH OF
AN INCH FOR MOST SPOTS. SOME OF THE HIGHER ELEVATION LOCATIONS HAVE
MEASURED AROUND ONE QUARTER INCH. MODELS REMAIN IN AGREEMENT THAT THE
FRONTAL BOUNDARY WILL PUSH ONSHORE THIS EVENING. AHEAD OF THE
FRONT...GUSTY SOUTH WINDS WILL INCREASE ACROSS THE COASTAL
AREAS...WITH GUSTS INTO THE 50-55 MPH RANGE THIS EVENING FOR THE MORE
EXPOSED BEACHES AND HEADLANDS.

THE SYSTEM TONIGHT WILL BRING A SHOT OF RAIN TONIGHT THROUGH EARLY
FRIDAY WITH AROUND AN INCH OF RAIN FOR THE COAST AND COAST
RANGE AND AROUND A HALF INCH FOR THE VALLEY. SNOW LEVELS WILL
GRADUALLY RISE A LITTLE THIS EVENING AHEAD OF THE FRONT...BUT LOWER
DOWN TO BELOW THE CASCADE PASSES BY EARLY FRIDAY MORNING AS THE COLD
UPPER TROUGH SLIDES OVER THE REGION. HOWEVER...THE BULK OF THE
PRECIPITATION WILL HAVE FINISHED BY THE TIME SNOW LEVELS COME DOWN.
OVERALL...A FEW INCHES OF SNOW AT THE PASSES ARE POSSIBLE WITH A FEW
ADDITIONAL INCHES OF SNOW AT THE HIGHER CASCADE ELEVATIONS. ADDED A
SLIGHT CHANCE OF THUNDERSTORMS TO THE FORECAST FOR THE COAST RANGE
AND POINTS WEST FOR EARLY TOMORROW MORNING. THE UPPER TROUGH MOVES
THROUGH THE AREA AND MODEL FORECAST SOUNDINGS INDICATE DECENT
INSTABILITY.

MODELS CONTINUE TO REMAIN IN GOOD AGREEMENT THAT A VERY MOIST
ATMOSPHERIC RIVER PATTERN WILL SET UP DIRECTING LARGE AMOUNTS OF
MOSITURE AT SW WASHINGTON AND NW OREGON THIS WEEKEND. HEAVY RAINFALL
LIKELY BEGINS BY EARLY SATURDAY MORNING AND CONTINUES THROUGH AT
LEAST SUNDAY. THE COAST RANGE...WILLAPA HILLS...CASCADES...AND
FOOTHILLS WILL LIKELY SEE ON THE ORDER OF 8 TO 12 INCHES OF RAINFALL.
LOCATIONS ON THE COAST MAY SEE 5 TO 7 INCHES OF RAIN...WHILE THE
INTERIOR VALLEY LOCATIONS CAN EXPECT 3 TO 4 INCHES. WHILE SOME
UNCERTAINTY IN THE PRECISE AREAS OF MAXIMUM RAINFALL
EXISTS...CONFIDENCE IS INCREASING THAT LARGE AMOUNTS OF PRECIPITATION
WILL OCCUR ACROSS THE FORECAST AREA WITH THIS SYSTEM. AS A
RESULT...THERE IS THE POTENTIAL FOR SHARP RISES ON AREA RIVERS AND
STREAMS THAT MAY RESULT IN FLOODING. SEE THE HYDROLOGY SECTION FOR
MORE DETAILS.

IN ADDITION...THOSE PLANNING TO BE ALONG THE COAST AT AREAS BEACHES
SHOULD CLOSELY MONITOR THE CONDITIONS FOR THIS WEEKEND. RAPIDLY
BUILDING SEAS WILL BRING THE POTENTIAL FOR DANGEROUS HIGH SURF ALONG
THE AREA BEACHES ON FRIDAY. LONG PERIOD SWELLS MAY REACH SHORE AND
SURPRISE INDIVIDUALS WHO ARE UNAWARE. ANYONE ON THE BEACHES SHOULD
EXERCISE EXTREME CAUTION AND AVOID THE SURF ZONE AS LARGE WAVES MAY
WASH OVER BEACHES AND JETTIES WITH LITTLE WARNING. SOME POTENTIAL FOR
MINOR TIDAL OVERFLOW IS POSSIBLE FOR SATURDAY AND SUNDAY...ESPECIALLY
AROUND HIGH TIDES. THIS THREAT COULD BE ENHANCED BY HIGH FLOWS ON
RIVERS IN RESPONSE TO THE RAINFALL THIS WEEKEND.  CULLEN

&&

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...MODELS AGREE THE
WEEKEND RAIN/FLOODING EVENT WILL WIND DOWN SUNDAY NIGHT INTO MONDAY.
A MUCH WEAKER FRONT MAY SLIDE SOUTHWARD ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON MONDAY NIGHT INTO TUESDAY. MODELS HAVE WAVERED
A BIT ON THIS SYSTEM SO POPS WERE GENERALLY KEPT IN THE HIGH END
CHANCE TO LOW END LIKELY. CONDITIONS SHOULD TEMPORARILY DRY OUT LATE
TUESDAY BEFORE A COLDER STORM SYSTEM BRINGS SHOWERS TO THE AREA ON
WEDNESDAY...BUT DISCREPANCIES CONTINUE AMONG THE MODELS. SNOW LEVELS
WILL LIKELY LOWER WELL BELOW PASS LEVEL SO HOLIDAY TRAVELERS HEADED
OVER THE CASCADE PASSES WILL CERTAINLY NEED TO MONITOR THE FORECAST.
COLD NORTHERLY WILL FOLLOW AND ALLOW TEMPERATURES TO COOL WELL BELOW
NORMAL AS CONDITIONS DRY OUT LATE WEEK. EASTERLY WINDS WILL LIKELY
RETURN. /NEUMAN

&&

.HYDROLOGY...SITUATION SETTING UP FOR A MEMORABLE HYDROLOGIC EVENT
MAINLY FOR LATER THIS WEEKEND AND HEADING INTO NEXT WEEK. STRONG AND
DEEP MOIST WESTERLY FLOW WILL BEGIN CROSSING THE PACNW COAST COME
SATURDAY MORNING. A VERY LONG FETCH OF MOISTURE IS STRETCHING ACROSS
THE PACIFIC WITH ORIGINS WEST TO THE SOUTH CHINA SEA. THIS MOIST AIR
MASS WILL BE PUSHED EAST BY A 150 TO 170 KT JET AND WESTERLY 25 TO
50 KT LOWER LEVEL WINDS. AS SUCH...THIS CONTINUES TO GIVE THE
APPEARANCE OF A CLASSIC HIGH PRECIPITATION ATMOSPHERIC RIVER EVENT
WHERE THE DEEP MOIST FLOW WILL SPEND A SIGNIFICANT AMOUNT OF TIME
ON A NEARLY PERPENDICULAR COURSE AGAINST THE COAST RANGE WITH THE
CASCADES TAKING A BIT HIGHER OF THE IMPACT. AS OF THE MORNING MODEL
RUNS AND RECENT NWRFC UPDATES...IT APPEARS MULTIPLE COAST RANGE
RIVERS HAVE A MODERATE POTENTIAL OF EXCEEDING FLOOD STAGE.
ADDITIONALLY...THIS EVENT HAS SUFFICIENT DEPTH TO BRING SIGNIFICANT
RAINS TO THE NORTH OREGON AND SOUTH WASHINGTON CASCADES WHERE RIVERS
WILL ALSO SEE POTENTIAL FOR NOTABLE FLOODING. WILL CONTINUE THE
HYDROLOGIC OUTLOOK (PDXESFPQR) PRODUCT HIGHLIGHTING CONCERNS. KEEP
IN MIND THAT DETAILS WILL ALWAYS BE IN FLUX UNDER THESE SCENARIOS AS
SUBTLE NORTH/SOUTH SHIFTS COLD MAKE DRAMATIC DIFFERENCES IN WHICH
BASINS RECEIVE EXTENDED PERIODS OF MODERATE TO HEAVY RAIN. PLEASE
CONTINUE TO FOLLOW THE LATEST FORECASTS AND IMPACTS AS CONDITIONS
WARRANT. RIVER FORECASTS ARE AVAILABLE ON OUR WEB PAGE AT:
HTTP://WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR (ALL LOWER CASE)

/JBONK

&&

.AVIATION...MIX OF VFR AND MVFR CIGS AND VIS THIS EVENING WILL
DROP TO MVFR/IFR AFTER MIDNIGHT. POST FRONTAL SHOWERS ACROSS THE
AREA WILL BRING DOWN CIGS AND VIS. WINDS AT KTTD GUSTING TO 30 KTS
WILL HELP KEEP CIGS UP AT KTTD AND POSSIBLY KPDX...THOUGH CIGS MAY
DROP TO MVFR/IFR WITH HEAVIER SHOWERS. RAIN TO CONTINUE THROUGH
THE DAY FRIDAY...WITH A CHANCE OF THUNDERSTORMS ALONG THE COAST
FRIDAY MORNING. CIGS AND VIS LIKELY TO IMPROVE TO A MIX OF VFR AND
MVFR BY FRIDAY AFTERNOON.

PDX AND APPROACHES...VFR CIGS LIKELY TO STAY VFR THIS
EVENING...WITH PERIODS OF MVFR CIGS AND VIS STARTING LATE THIS
EVENING BEHIND THE COLD FRONT. CIGS AND VIS LIKELY TO DROP TO
MVFR/IFR EARLY FRIDAY MORNING...BUT IMPROVE TO VFR BY FRIDAY
AFTERNOON. -MCCOY

&&

.MARINE...COMBINED SEAS AROUND 12 FT BUILDING TO 14 TO 16 FT BY
FRIDAY MORNING. SEAS WILL RAPIDLY BUILD DURING THE AFTERNOON HOURS AS
THE 20 TO 22 FT SWELL APPROACHES...BRINGING SEAS UP TO 22 FT BY
FRIDAY EVENING. SEAS WILL REMAIN AROUND 20 TO 22 FT THROUGH
SATURDAY MORNING. AS THE SWELL BEGINS TO DROP OFF...SOUTHERLY
WINDS INCREASE AHEAD OF OUR NEXT STRONG COLD FRONT. GALES LOOK
LIKELY WITH THIS SYSTEM...KEEPING SEAS AROUND 20 TO 22 FT THROUGH
SATURDAY MORNING. SEAS BEGIN TO DROP BELOW 20 FT SATURDAY
AFTERNOON BEHIND THE FRONT...AS WINDS EASE...BUT SEAS WILL STAY IN
THE UPPER TEENS THROUGH SUNDAY EVENING.

ANOTHER WEAK FRONTAL SYSTEM COULD KEEP SMALL CRAFT WINDS ACROSS
OUR SOUTHERN WATERS THROUGH SUNDAY NIGHT. OTHERWISE...RELATIVELY
BENIGN WEATHER EXPECTED EARLY NEXT WEEK AS HIGH PRESSURE BUILDS
OVER THE WATERS. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 10 AM FRIDAY TO 4 AM PST SATURDAY FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...HIGH SURF ADVISORY FROM 10 AM FRIDAY TO 4 AM PST SATURDAY FOR
     SOUTH WASHINGTON COAST.

PZ...GALE WARNING UNTIL MIDNIGHT PST TONIGHT FOR COASTAL WATERS FROM
     CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 3 PM PST
     SUNDAY.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.


  [top]

000
FXUS66 KOTX 182307
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
307 PM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue into early next week.
Another weather system will bring snow to the mountains with
mainly rain for the valleys tonight into Friday. A stronger storm
Saturday into Sunday will bring mainly rain for the valleys...as
well as mountain snow with rising snow levels. Temperatures are
expected to remain above average through early next week...before
dropping down towards normal values by Christmas Day.

&&

.DISCUSSION...
Tonight and Friday...There is good model agreement of an occluded
front tracking into Central and Eastern Washington
tonight...reaching North Idaho Friday morning. There is good model
agreement of this system bringing widespread precipitation to the
region due to a combination of isentropic lift...an already moist
low level air mass...as well as upper jet support with a south-
north jet oriented parallel to the front. Isentropic ascent will
be maximized in the Cascades and northern mountains with low level
upslope flow into these areas as well. However this is a quick
moving front...with models generating anywhere between a tenth to
a quarter inch of liquid with locally up to a half inch over the
high terrain of the northern mountains. Based on current wet bulb
temperatures and model snow levels with this system...most valley
areas will see rain with snow in the mountains. Exception is the
Methow Valley where expected low temps near 32F should allow for
2-3 inches of snow. Republic may also see light accumulations with
expected snow levels in the Okanogan Highlands between 2000-2500
feet. The mountains will pick up 3 to 6 inches of snow with this
system with winter driving conditions likely over the mountain
passes.  JW

...Major storm expected to dump heavy precipitation and heavy
mountain snows to portions of the Inland NW this weekend...

Saturday through Monday...Confidence is still very good that a
very impressive atmospheric river will impact the region through
much of this period. As of 2pm...the leading edge of the river was
located just west of 160w and moving steadily eastward. Most model
solutions take the leading edge of this moisture onto the
Washington coast early Saturday morning and into the Cascades
before midday. It will then cross the remainder of the forecast
area during the day with the passage of a strong warm front. The
atmospheric river will generally remain locked over the region
through Sunday. Strong isentropic ascent associated with the warm
front will spell measurable precipitation for all locations on
Saturday. Then the mid-level warm air advection will either cease
or weaken sometime late Saturday evening resulting in a developing
rain shadow which will either end the threat of precipitation in
the lee of the Cascades or at least significantly lower the
chances. This would affect Wenatchee, the Columbia Basin, Okanogan
Valleys and to a lesser extent the Palouse and Spokane area.
Meanwhile moderate orographic ascent from low-level west-southwest
winds will keep persistent precipitation going over most of the
Idaho Panhandle and near the crest. Whether or not the
precipitation rates pick up again on Sunday or Monday in the lee
of the Cascades is questionable. The NAM shows a strong enough
shortwave trough to lift the atmospheric river northward on Sunday
resulting in another round of precipitation, albeit significantly
lighter than that which falls on Saturday. By Monday the plume of
moisture is expected to sag south of the Oregon/Washington border
with precipitation rates falling off over most areas...however
residual precipitation will likely continue mainly over the
mountains...especially over SE Washington the southern Cascades
and the southern Idaho Panhandle. So from an impact standpoint
here`s what we are expecting.

*Precipitation type and amounts...this is likely the most
 difficult part of this forecast. Our confidence is quite high
 that significant precipitation will fall. Total precipitation
 amounts near the Cascade crest will likely range from 1.5-3.0
 inches and anywhere from 0.75-1.50 inches over the Panhandle
 Mountains. Meanwhile totals across the remainder of the forecast
 area will generally range from 0.40-1.00 inches. If the
 atmospheric river decided to remain fixed over our area...instead
 of slowly sagging south these values would undoubtedly need to be
 raised. Instead it looks like the brunt of the river will focus
 on points south of our forecast area...but not by much. As for
 precipitation type that is easily the toughest part of this
 forecast. Not necessarily for the mountains, but for the valleys,
 mainly in the Cascades. Initially snow levels will be close to
 the valley floors near the Cascades but they should steadily rise
 through the weekend. By Sunday we will be looking at snow levels
 ranging from nearly 4k feet near the Canadian border to almost 7k
 feet near the Oregon border. The models have been too cool across
 most of the forecast area lately and not sure this trend will end
 anytime soon. The models have unquestionable snow for most of the
 Cascades at the onset of the event on Saturday morning as they
 have surface temps in the lower to middle 20s. We think that`s
 too cold but is it 10 degrees too cold? That is not likely the
 case, however even if they are 5 degrees too cold it won`t take
 much warming to make accumulating snow tough to come by. If the
 precipitation rates are high enough that can be overcome though.
 So locations such as the Methow Valley could very well see
 moderate to heavy snows through at least early Saturday evening
 with moderate amounts possible. Farther south at Leavenworth and
 Plain there would be a much tougher time as the temperatures
 should be a little bit warmer. The critical thing could be how
 cool will temperatures get on Friday night/early Saturday. When
 we know that answer we could issue the appropriate weather
 highlights, if any. For now we will address via weather stories.
 Meanwhile our confidence is growing that locations that have an
 easier time of mixing with a dynamic warm fronts, such as the
 Waterville Plateau or Okanogan Valley, will see much less snow.
 Even valleys near the Canadian Border may not see much snow. So
 this looks like it will mainly be a mountain event...with some of
 the Cascade elevations above 4000 feet seeing up to 2 feet of
 snow by Sunday afternoon. We expect to initially see snow over
 the major passes on Saturday but there should be a changeover
 sometime during the day. Again it looks like snow and
 precipitation rates will steadily decline on Sunday night/Monday.

*Winds and temperatures...This will be a very strong system with
 850 mb winds climbing into the 40-50 kt range. Whether or not
 these fully mix down to the ground isn`t certain. Cold fronts are
 much more efficient at this downward mixing. Meanwhile the
 surface pressure gradient isn`t all that impressive on Sunday or
 Monday, which is when we`d expect the strongest winds. So this
 leads us to think it could be breezy on Sunday and Monday but
 nothing extraordinary. Meanwhile temperatures will be unusually
 warm once again. Highs on Sunday will be in the mid 40s to mid
 50s over much of the region...with cooler temperatures near the
 Canadian border and Cascades. Monday will be a little
 cooler...but not by much. So whatever snow falls on Saturday over
 valley locations will have a good chance of melting, at least
 part of it especially considering nighttime lows will be above
 freezing as well. fx


Monday night through Thursday: A change in the large scale pattern
weather pattern is almost certain during this time-frame. For
several days, models continue to indicate a transition from mild
and wet weather toward drier and cooler. How fast this transition
occurs carries moderate to high uncertainty. Consequently, this
will have moderate ramifications on precipitation chances,
amounts, and type largely within the Monday night to Wednesday
time-frame. The atmospheric river or plume of subtropical moisture
starts off over the region Monday night night and sags southward
Tuesday into Tuesday night as yet another trof of low pressure
suppresses the large scale ridge in place. Generally, speaking
most valleys will continue to experience rain with mid to high
mountain snows given the origins of the moisture tap and
accompanying 850mb temperatures between -1 and 4C. Some models
indicate a weaker wave ahead of the main trof...and these features
will bring some fluctuations to mountain snow levels and potential
for wintry impacts on the mountain passes. The potential for any
valley snow will arrive during the Tuesday night into Wednesday
time-frame (Christmas Eve) as the ridge finally gives way to
northwest flow and a stronger shortwave trof. This will allow much
cooler air (not arctic by any means) to move back into the region
accompanied by 850mb temps of -1 to -4C. Generally speaking, the
deeper moisture will be shoved southward and the cooler air will
be drier however, there is a good chance that the cooler air
clashes with the moisture and leads to a period of lower elevation
snowfall. Model trends continue to push this heavier band south
and south each run suggesting the best chances near the Blue Mtns,
Camas Prairie, lower ID Panhandle, and perhaps the Palouse...but I
think there is enough uncertainty at this time to completely rule
out the potential for some smaller scale bands to pass through
just about any valley location as the air masses change. What is a
strong possibility is snow on the mountain passes, a period of
gusty winds, and transition back to seasonal temperatures. We will
continue to update you on the potential for valley snow as
confidence increases during this busy holiday period. /sb

&&

.AVIATION...
18Z TAFS: A saturated boundary layer north and west of KPUW will
result in widespread IFR/MVFR stratus over the Columbia Basin,
Spokane/Coeur D`Alene area extending north to the Canadian border
and west into the Cascade crest. The stratus should lift a bit
into the afternoon per forecast soundings. A drier boundary layer
over KPUW/KLWS will lead to continued VFR conditions. The next
weather system will spread -RA across the TAF sites overnight into
Friday morning with a mix of IFR and MVFR conditions.  JW


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        36  41  33  40  38  45 /  70 100  10  90  90  60
Coeur d`Alene  35  40  33  38  35  43 /  50 100  20  90  90  70
Pullman        37  43  34  40  39  48 /  70 100  10  90  90  80
Lewiston       38  47  34  44  42  51 /  40  70  10  80 100  70
Colville       35  40  33  37  35  41 / 100 100  20 100  90  70
Sandpoint      33  38  32  37  34  39 /  50 100  30  80  90  80
Kellogg        33  37  31  37  34  40 /  40 100  40  70 100 100
Moses Lake     37  45  34  40  39  47 /  90  50  10  90  60  30
Wenatchee      35  43  32  36  36  43 /  80  30  10  90  70  40
Omak           35  39  30  34  34  38 / 100  80  10  90  80  30

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 182307
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
307 PM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue into early next week.
Another weather system will bring snow to the mountains with
mainly rain for the valleys tonight into Friday. A stronger storm
Saturday into Sunday will bring mainly rain for the valleys...as
well as mountain snow with rising snow levels. Temperatures are
expected to remain above average through early next week...before
dropping down towards normal values by Christmas Day.

&&

.DISCUSSION...
Tonight and Friday...There is good model agreement of an occluded
front tracking into Central and Eastern Washington
tonight...reaching North Idaho Friday morning. There is good model
agreement of this system bringing widespread precipitation to the
region due to a combination of isentropic lift...an already moist
low level air mass...as well as upper jet support with a south-
north jet oriented parallel to the front. Isentropic ascent will
be maximized in the Cascades and northern mountains with low level
upslope flow into these areas as well. However this is a quick
moving front...with models generating anywhere between a tenth to
a quarter inch of liquid with locally up to a half inch over the
high terrain of the northern mountains. Based on current wet bulb
temperatures and model snow levels with this system...most valley
areas will see rain with snow in the mountains. Exception is the
Methow Valley where expected low temps near 32F should allow for
2-3 inches of snow. Republic may also see light accumulations with
expected snow levels in the Okanogan Highlands between 2000-2500
feet. The mountains will pick up 3 to 6 inches of snow with this
system with winter driving conditions likely over the mountain
passes.  JW

...Major storm expected to dump heavy precipitation and heavy
mountain snows to portions of the Inland NW this weekend...

Saturday through Monday...Confidence is still very good that a
very impressive atmospheric river will impact the region through
much of this period. As of 2pm...the leading edge of the river was
located just west of 160w and moving steadily eastward. Most model
solutions take the leading edge of this moisture onto the
Washington coast early Saturday morning and into the Cascades
before midday. It will then cross the remainder of the forecast
area during the day with the passage of a strong warm front. The
atmospheric river will generally remain locked over the region
through Sunday. Strong isentropic ascent associated with the warm
front will spell measurable precipitation for all locations on
Saturday. Then the mid-level warm air advection will either cease
or weaken sometime late Saturday evening resulting in a developing
rain shadow which will either end the threat of precipitation in
the lee of the Cascades or at least significantly lower the
chances. This would affect Wenatchee, the Columbia Basin, Okanogan
Valleys and to a lesser extent the Palouse and Spokane area.
Meanwhile moderate orographic ascent from low-level west-southwest
winds will keep persistent precipitation going over most of the
Idaho Panhandle and near the crest. Whether or not the
precipitation rates pick up again on Sunday or Monday in the lee
of the Cascades is questionable. The NAM shows a strong enough
shortwave trough to lift the atmospheric river northward on Sunday
resulting in another round of precipitation, albeit significantly
lighter than that which falls on Saturday. By Monday the plume of
moisture is expected to sag south of the Oregon/Washington border
with precipitation rates falling off over most areas...however
residual precipitation will likely continue mainly over the
mountains...especially over SE Washington the southern Cascades
and the southern Idaho Panhandle. So from an impact standpoint
here`s what we are expecting.

*Precipitation type and amounts...this is likely the most
 difficult part of this forecast. Our confidence is quite high
 that significant precipitation will fall. Total precipitation
 amounts near the Cascade crest will likely range from 1.5-3.0
 inches and anywhere from 0.75-1.50 inches over the Panhandle
 Mountains. Meanwhile totals across the remainder of the forecast
 area will generally range from 0.40-1.00 inches. If the
 atmospheric river decided to remain fixed over our area...instead
 of slowly sagging south these values would undoubtedly need to be
 raised. Instead it looks like the brunt of the river will focus
 on points south of our forecast area...but not by much. As for
 precipitation type that is easily the toughest part of this
 forecast. Not necessarily for the mountains, but for the valleys,
 mainly in the Cascades. Initially snow levels will be close to
 the valley floors near the Cascades but they should steadily rise
 through the weekend. By Sunday we will be looking at snow levels
 ranging from nearly 4k feet near the Canadian border to almost 7k
 feet near the Oregon border. The models have been too cool across
 most of the forecast area lately and not sure this trend will end
 anytime soon. The models have unquestionable snow for most of the
 Cascades at the onset of the event on Saturday morning as they
 have surface temps in the lower to middle 20s. We think that`s
 too cold but is it 10 degrees too cold? That is not likely the
 case, however even if they are 5 degrees too cold it won`t take
 much warming to make accumulating snow tough to come by. If the
 precipitation rates are high enough that can be overcome though.
 So locations such as the Methow Valley could very well see
 moderate to heavy snows through at least early Saturday evening
 with moderate amounts possible. Farther south at Leavenworth and
 Plain there would be a much tougher time as the temperatures
 should be a little bit warmer. The critical thing could be how
 cool will temperatures get on Friday night/early Saturday. When
 we know that answer we could issue the appropriate weather
 highlights, if any. For now we will address via weather stories.
 Meanwhile our confidence is growing that locations that have an
 easier time of mixing with a dynamic warm fronts, such as the
 Waterville Plateau or Okanogan Valley, will see much less snow.
 Even valleys near the Canadian Border may not see much snow. So
 this looks like it will mainly be a mountain event...with some of
 the Cascade elevations above 4000 feet seeing up to 2 feet of
 snow by Sunday afternoon. We expect to initially see snow over
 the major passes on Saturday but there should be a changeover
 sometime during the day. Again it looks like snow and
 precipitation rates will steadily decline on Sunday night/Monday.

*Winds and temperatures...This will be a very strong system with
 850 mb winds climbing into the 40-50 kt range. Whether or not
 these fully mix down to the ground isn`t certain. Cold fronts are
 much more efficient at this downward mixing. Meanwhile the
 surface pressure gradient isn`t all that impressive on Sunday or
 Monday, which is when we`d expect the strongest winds. So this
 leads us to think it could be breezy on Sunday and Monday but
 nothing extraordinary. Meanwhile temperatures will be unusually
 warm once again. Highs on Sunday will be in the mid 40s to mid
 50s over much of the region...with cooler temperatures near the
 Canadian border and Cascades. Monday will be a little
 cooler...but not by much. So whatever snow falls on Saturday over
 valley locations will have a good chance of melting, at least
 part of it especially considering nighttime lows will be above
 freezing as well. fx


Monday night through Thursday: A change in the large scale pattern
weather pattern is almost certain during this time-frame. For
several days, models continue to indicate a transition from mild
and wet weather toward drier and cooler. How fast this transition
occurs carries moderate to high uncertainty. Consequently, this
will have moderate ramifications on precipitation chances,
amounts, and type largely within the Monday night to Wednesday
time-frame. The atmospheric river or plume of subtropical moisture
starts off over the region Monday night night and sags southward
Tuesday into Tuesday night as yet another trof of low pressure
suppresses the large scale ridge in place. Generally, speaking
most valleys will continue to experience rain with mid to high
mountain snows given the origins of the moisture tap and
accompanying 850mb temperatures between -1 and 4C. Some models
indicate a weaker wave ahead of the main trof...and these features
will bring some fluctuations to mountain snow levels and potential
for wintry impacts on the mountain passes. The potential for any
valley snow will arrive during the Tuesday night into Wednesday
time-frame (Christmas Eve) as the ridge finally gives way to
northwest flow and a stronger shortwave trof. This will allow much
cooler air (not arctic by any means) to move back into the region
accompanied by 850mb temps of -1 to -4C. Generally speaking, the
deeper moisture will be shoved southward and the cooler air will
be drier however, there is a good chance that the cooler air
clashes with the moisture and leads to a period of lower elevation
snowfall. Model trends continue to push this heavier band south
and south each run suggesting the best chances near the Blue Mtns,
Camas Prairie, lower ID Panhandle, and perhaps the Palouse...but I
think there is enough uncertainty at this time to completely rule
out the potential for some smaller scale bands to pass through
just about any valley location as the air masses change. What is a
strong possibility is snow on the mountain passes, a period of
gusty winds, and transition back to seasonal temperatures. We will
continue to update you on the potential for valley snow as
confidence increases during this busy holiday period. /sb

&&

.AVIATION...
18Z TAFS: A saturated boundary layer north and west of KPUW will
result in widespread IFR/MVFR stratus over the Columbia Basin,
Spokane/Coeur D`Alene area extending north to the Canadian border
and west into the Cascade crest. The stratus should lift a bit
into the afternoon per forecast soundings. A drier boundary layer
over KPUW/KLWS will lead to continued VFR conditions. The next
weather system will spread -RA across the TAF sites overnight into
Friday morning with a mix of IFR and MVFR conditions.  JW


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        36  41  33  40  38  45 /  70 100  10  90  90  60
Coeur d`Alene  35  40  33  38  35  43 /  50 100  20  90  90  70
Pullman        37  43  34  40  39  48 /  70 100  10  90  90  80
Lewiston       38  47  34  44  42  51 /  40  70  10  80 100  70
Colville       35  40  33  37  35  41 / 100 100  20 100  90  70
Sandpoint      33  38  32  37  34  39 /  50 100  30  80  90  80
Kellogg        33  37  31  37  34  40 /  40 100  40  70 100 100
Moses Lake     37  45  34  40  39  47 /  90  50  10  90  60  30
Wenatchee      35  43  32  36  36  43 /  80  30  10  90  70  40
Omak           35  39  30  34  34  38 / 100  80  10  90  80  30

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




  [top]

000
FXUS66 KSEW 182254 AAA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAIN AND LOCALLY WINDY CONDITIONS TO
WESTERN WASHINGTON THROUGH TONIGHT. AN UPPER LEVEL TROUGH WILL BRING
SCATTERED SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE
NORTHEAST PACIFIC WILL BRING WIND AND RAIN INTO WESTERN WASHINGTON
THIS WEEKEND. A BROAD UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION
EARLY NEXT WEEK FOR NOT QUITE AS WET WEATHER. COOLER TEMPERATURES
ARE POSSIBLE BY MID WEEK.

&&

.SHORT TERM...WARM ADVECTION RAIN IS FILLING IN ACROSS WRN WA THIS
AFTERNOON. VISIBLE SATELLITE IMAGERY IMPLIES THE SURFACE FRONT IS
NOW JUST INSIDE 130 W HEADING TOWARD WRN WA. IR/WV IMAGERY SHOWS A
WAVE FORMING ON THE SRN EXTENT OF THE FRONTAL BAND AS IT BEGINS TO
SPLIT. THIS WILL SLOW THE PROGRESS OF THE SYSTEM EWD BUT ALSO RESULT
IN WEAKER FLOW ALOFT SO OROGRAPHICS WILL NOT PLAY AS BIG A ROLE AS
USUAL. MODELS STILL SHOW 12 HOUR QPF TOTALS RANGING FROM ROUGHLY ONE
HALF TO ONE INCH LIQUID WITH LOCALLY HIGHER AMOUNTS. PLACES WHERE
THIS FALLS AS ALL SNOW COULD SEE UP TO 1 FOOT. SOME OF THE HIGHER
SKI RESORTS AND S/SW FACING SLOPES ARE MOST LIKELY TO SEE THESE TYPE
OF SNOW TOTALS. THE SNOW LEVEL IS DIFFICULT TO PINPOINT WITH THIS
SYSTEM WITH SOME FLUCTUATION LIKELY BETWEEN 3500 AND 5000 FEET.
TEMPERATURES IN MOST PASSES ARE STILL IN THE UPPER 20S TO AROUND 30
DEGREES...SO PRECIPITATION WILL LIKELY START AS SNOW EVEN AT
SNOQUALMIE PASS. A COUPLE INCHES MAY FALL...THEN SNOW LEVELS SHOULD
GENERALLY START TO RISE AS WARMER AIR STARTS TO WORK INLAND. THE
MAIN SNOW LEVEL SHOULD HOVER AROUND 4500 TO 5000 FEET TONIGHT WHICH
PUTS STEVENS PASS ON THE EDGE. UP TO 6 INCHES STILL SEEMS POSSIBLE
DEPENDING ON HOW MUCH RAIN MIXES IN. SNOW LEVELS WILL FALL BACK DOWN
TO AROUND 3000 FEET BEHIND THE FRONT BUT ONLY MINOR ADDITIONAL
ACCUMULATIONS EXPECTED FRIDAY MORNING.

SE PRESSURE GRADIENTS WILL CONTINUE TO TIGHTEN THIS EVENING. SE
WINDS IN THE ADMIRALTY INLET AREA AND SAN JUANS ARE CURRENTLY
GUSTING INTO THE LOW 30 MPH RANGE AND SHOULD PICK UP CONSIDERABLY
THIS EVENING. THE WIND ADVISORY WILL REMAIN IN PLACE FOR GUSTS TO 45
MPH ACROSS THE N INTERIOR...EXCLUDING WRN SKAGIT COUNTY. STRONGEST
WINDS WILL BE ALONG THE WATER AND AT PLACES EXPOSED TO SE WINDS. THE
WIND ADVISORY RUNS THROUGH MIDNIGHT TONIGHT.

IT WILL BE COOL AND SHOWERY ON FRIDAY AS THE FRONT MOVES E AND AN
UPPER TROUGH REACHES THE AREA. COLD TOPPED CU OFFSHORE INDICATES
UNSTABLE CONDITIONS BEHIND THE TROUGH. MODEL LI`S ARE NEGATIVE OVER
THE COASTAL WATERS BUT NOT OVER THE LAND AREAS. BUFFER FORECAST
SOUNDINGS SHOW THE UNSTABLE LAYER CAPPED AT 700 MB SO THUNDERSTORMS
WOULD SEEM UNLIKELY.

STRONG AND MOIST WLY FLOW DRIVEN BY A STRONG 180+ KT JET WILL STEER
A WARM FRONT INTO WRN WA ON SATURDAY. TIMING IS A LITTLE FASTER WITH
MOST MODELS DEVELOPING WIDESPREAD RAIN ACROSS WRN WA BY LATE FRIDAY
NIGHT OR EARLY SATURDAY MORNING. INITIALLY THE FLOW WILL BE OUT OF
THE S/SW AND STRONG AT 40 TO 50 KT. THIS WILL PRODUCE HEFTY
OROGRAPHICALLY ENHANCED RAINFALL AMOUNTS ALONG S/SW FACING SLOPES OF
THE OLYMPICS AND CASCADES. THIS WILL ALMOST CERTAINLY CAUSE FLOODING
ON THE SKOKOMISH RIVER BY LATER SATURDAY NIGHT. THE FLOW TURNS MORE
WLY SATURDAY NIGHT AND SUNDAY WHICH IS A FAVORABLE DIRECTION FOR
HEAVY RAIN IN MORE BASINS ACROSS THE W SLOPES OF THE CASCADES. THIS
WILL CAUSE ADDITIONAL FLOOD CONCERNS. REFER TO THE EXTENDED FLOOD
OUTLOOK STATEMENT AND HYDRO DISCUSSION BELOW FOR FURTHER DETAILS.

THIS NEXT SYSTEM WILL ALSO HAVE STRONGER SE PRESSURE GRADIENTS AND
STRONGER FLOW ALOFT AHEAD OF THE COLD FRONT ON SATURDAY. MESO MODELS
ARE SHOWING HIGH END ADVISORY LEVEL TYPE WINDS BUT HIGH WIND IN A
COUPLE SPOTS CANNOT BE RULED OUT EITHER. THIS IS STILL A COUPLE DAYS
OUT AND WILL OPT TO MAINTAIN A HIGH END ADVISORY WIND FORECAST FOR
THE COAST/N INTERIOR. PUGET SOUND WILL ALSO BECOME
BREEZY...ESPECIALLY AS GRADIENTS BECOME MORE SLY SATURDAY NIGHT AND
SUNDAY. BUT FORECAST GRADIENTS DO NOT SEEM TO SUPPORT EVEN ADVISORY
LEVEL WINDS FOR PUGET SOUND AT THIS TIME.

THE BAROCLINIC BOUNDARY WILL START TO DRIFT SWD SUNDAY AFTERNOON
DIRECTING THE HEAVIEST PRECIPITATION INTO THE WA CASCADES FROM
ABOUT KING COUNTY SWD INTO THE N/CENTRAL OREGON CASCADES. THIS WILL
HELP MITIGATE FLOODING CONCERNS ACROSS THE FAR N ALTHOUGH DETAILS ON
WHERE THIS BOUNDARY SETS UP REMAINS UNCERTAIN. THERE DOES SEEM TO BE
PRETTY GOOD CONSENSUS EVOLVING AMONG THE MODELS THAT THE HEAVY
MOUNTAIN RAIN WILL TAPER OFF FROM N TO S ON SUNDAY AND MOSTLY SHUT
OFF BY SUNDAY NIGHT AS THE RIDGE BEGINS TO BUILD.

.LONG TERM...THE EXTENDED FORECAST REMAINS CHALLENGING WITH A WIDE
RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME AGREEMENT THAT
MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN RAINFALL AS
HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE STRENGTH OR
TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON TUESDAY. THE
LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH WOULD STILL
PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH NOT AS MUCH
AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY BEHIND THE FRONT.

AT 2230Z A STRONG FRONT WAS MOVING THROUGH THE OFFSHORE WATERS. IT
WILL PUSH ACROSS THE AREA REACHING THE INTERIOR VALLEYS ABOUT 08Z
FRIDAY THEN EAST OF THE CASCADES BY 12Z. LOW END VFR CONDITIONS THIS
AFTERNOON WILL DETERIORATE TO MVFR SHORTLY AFTER 00Z THIS EVENING AS
PRECIPITATION INCREASES WITH THE APPROACH OF THE FRONT.

THERE IS LIKELY TO BE A PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD AND ALONG THE COAST FOR A FEW
HOURS AHEAD OF THE FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40-50KT
AND SURFACE WINDS REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC035-040 WITH PERIODS OF LIGHT RAIN...WITH
CEILINGS DETERIORATING TO OVC015 BY 06Z. SE WIND 7-11 KT WILL SHIFT
TO S 11-17 KT WITH GUSTS TO 25 KT BEHIND THE FRONT 08Z-10Z. THERE
WILL BE 2-4 HOURS OF WIND 19035-40KT AT FL020 AHEAD OF THE INCOMING
FRONT ABOUT 05Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 970 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE WATERS TONIGHT. GALE FORCE WINDS CAN BE
EXPECTED OVER THE COASTAL WATERS AND AT THE EAST ENTRANCE TO THE
STRAIT UNTIL THE FRONT PASSES WITH SMALL CRAFT ADVISORY CONDITIONS
FOR THE STRAIT...NORTHERN INLAND WATERS...ADMIRALTY INLET AND PUGET
SOUND AND HOOD CANAL.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-25 FT SWELL THAT WILL REACH THE COAST
MIDDAY FRIDAY AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY. TIDAL
ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH
TIDE OCCURS SATURDAY MORNING. SOME COASTAL FLOODING IS POSSIBLE
ALONG THE COAST AROUND THE HIGH TIDE ON SATURDAY...AND A COASTAL
FLOOD WATCH IS IN EFFECT. A HIGH SURF ADVISORY WAS ISSUED FOR THE
COAST FROM MIDDAY FRIDAY THROUGH FRIDAY NIGHT.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. STRONG ONSHORE FLOW
SATURDAY NIGHT WILL SLOWLY DIMINISH ON SUNDAY. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST
     ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.




&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML


















000
FXUS66 KSEW 182254 AAA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST THU DEC 18 2014

.SYNOPSIS...A FRONT WILL BRING RAIN AND LOCALLY WINDY CONDITIONS TO
WESTERN WASHINGTON THROUGH TONIGHT. AN UPPER LEVEL TROUGH WILL BRING
SCATTERED SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE
NORTHEAST PACIFIC WILL BRING WIND AND RAIN INTO WESTERN WASHINGTON
THIS WEEKEND. A BROAD UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION
EARLY NEXT WEEK FOR NOT QUITE AS WET WEATHER. COOLER TEMPERATURES
ARE POSSIBLE BY MID WEEK.

&&

.SHORT TERM...WARM ADVECTION RAIN IS FILLING IN ACROSS WRN WA THIS
AFTERNOON. VISIBLE SATELLITE IMAGERY IMPLIES THE SURFACE FRONT IS
NOW JUST INSIDE 130 W HEADING TOWARD WRN WA. IR/WV IMAGERY SHOWS A
WAVE FORMING ON THE SRN EXTENT OF THE FRONTAL BAND AS IT BEGINS TO
SPLIT. THIS WILL SLOW THE PROGRESS OF THE SYSTEM EWD BUT ALSO RESULT
IN WEAKER FLOW ALOFT SO OROGRAPHICS WILL NOT PLAY AS BIG A ROLE AS
USUAL. MODELS STILL SHOW 12 HOUR QPF TOTALS RANGING FROM ROUGHLY ONE
HALF TO ONE INCH LIQUID WITH LOCALLY HIGHER AMOUNTS. PLACES WHERE
THIS FALLS AS ALL SNOW COULD SEE UP TO 1 FOOT. SOME OF THE HIGHER
SKI RESORTS AND S/SW FACING SLOPES ARE MOST LIKELY TO SEE THESE TYPE
OF SNOW TOTALS. THE SNOW LEVEL IS DIFFICULT TO PINPOINT WITH THIS
SYSTEM WITH SOME FLUCTUATION LIKELY BETWEEN 3500 AND 5000 FEET.
TEMPERATURES IN MOST PASSES ARE STILL IN THE UPPER 20S TO AROUND 30
DEGREES...SO PRECIPITATION WILL LIKELY START AS SNOW EVEN AT
SNOQUALMIE PASS. A COUPLE INCHES MAY FALL...THEN SNOW LEVELS SHOULD
GENERALLY START TO RISE AS WARMER AIR STARTS TO WORK INLAND. THE
MAIN SNOW LEVEL SHOULD HOVER AROUND 4500 TO 5000 FEET TONIGHT WHICH
PUTS STEVENS PASS ON THE EDGE. UP TO 6 INCHES STILL SEEMS POSSIBLE
DEPENDING ON HOW MUCH RAIN MIXES IN. SNOW LEVELS WILL FALL BACK DOWN
TO AROUND 3000 FEET BEHIND THE FRONT BUT ONLY MINOR ADDITIONAL
ACCUMULATIONS EXPECTED FRIDAY MORNING.

SE PRESSURE GRADIENTS WILL CONTINUE TO TIGHTEN THIS EVENING. SE
WINDS IN THE ADMIRALTY INLET AREA AND SAN JUANS ARE CURRENTLY
GUSTING INTO THE LOW 30 MPH RANGE AND SHOULD PICK UP CONSIDERABLY
THIS EVENING. THE WIND ADVISORY WILL REMAIN IN PLACE FOR GUSTS TO 45
MPH ACROSS THE N INTERIOR...EXCLUDING WRN SKAGIT COUNTY. STRONGEST
WINDS WILL BE ALONG THE WATER AND AT PLACES EXPOSED TO SE WINDS. THE
WIND ADVISORY RUNS THROUGH MIDNIGHT TONIGHT.

IT WILL BE COOL AND SHOWERY ON FRIDAY AS THE FRONT MOVES E AND AN
UPPER TROUGH REACHES THE AREA. COLD TOPPED CU OFFSHORE INDICATES
UNSTABLE CONDITIONS BEHIND THE TROUGH. MODEL LI`S ARE NEGATIVE OVER
THE COASTAL WATERS BUT NOT OVER THE LAND AREAS. BUFFER FORECAST
SOUNDINGS SHOW THE UNSTABLE LAYER CAPPED AT 700 MB SO THUNDERSTORMS
WOULD SEEM UNLIKELY.

STRONG AND MOIST WLY FLOW DRIVEN BY A STRONG 180+ KT JET WILL STEER
A WARM FRONT INTO WRN WA ON SATURDAY. TIMING IS A LITTLE FASTER WITH
MOST MODELS DEVELOPING WIDESPREAD RAIN ACROSS WRN WA BY LATE FRIDAY
NIGHT OR EARLY SATURDAY MORNING. INITIALLY THE FLOW WILL BE OUT OF
THE S/SW AND STRONG AT 40 TO 50 KT. THIS WILL PRODUCE HEFTY
OROGRAPHICALLY ENHANCED RAINFALL AMOUNTS ALONG S/SW FACING SLOPES OF
THE OLYMPICS AND CASCADES. THIS WILL ALMOST CERTAINLY CAUSE FLOODING
ON THE SKOKOMISH RIVER BY LATER SATURDAY NIGHT. THE FLOW TURNS MORE
WLY SATURDAY NIGHT AND SUNDAY WHICH IS A FAVORABLE DIRECTION FOR
HEAVY RAIN IN MORE BASINS ACROSS THE W SLOPES OF THE CASCADES. THIS
WILL CAUSE ADDITIONAL FLOOD CONCERNS. REFER TO THE EXTENDED FLOOD
OUTLOOK STATEMENT AND HYDRO DISCUSSION BELOW FOR FURTHER DETAILS.

THIS NEXT SYSTEM WILL ALSO HAVE STRONGER SE PRESSURE GRADIENTS AND
STRONGER FLOW ALOFT AHEAD OF THE COLD FRONT ON SATURDAY. MESO MODELS
ARE SHOWING HIGH END ADVISORY LEVEL TYPE WINDS BUT HIGH WIND IN A
COUPLE SPOTS CANNOT BE RULED OUT EITHER. THIS IS STILL A COUPLE DAYS
OUT AND WILL OPT TO MAINTAIN A HIGH END ADVISORY WIND FORECAST FOR
THE COAST/N INTERIOR. PUGET SOUND WILL ALSO BECOME
BREEZY...ESPECIALLY AS GRADIENTS BECOME MORE SLY SATURDAY NIGHT AND
SUNDAY. BUT FORECAST GRADIENTS DO NOT SEEM TO SUPPORT EVEN ADVISORY
LEVEL WINDS FOR PUGET SOUND AT THIS TIME.

THE BAROCLINIC BOUNDARY WILL START TO DRIFT SWD SUNDAY AFTERNOON
DIRECTING THE HEAVIEST PRECIPITATION INTO THE WA CASCADES FROM
ABOUT KING COUNTY SWD INTO THE N/CENTRAL OREGON CASCADES. THIS WILL
HELP MITIGATE FLOODING CONCERNS ACROSS THE FAR N ALTHOUGH DETAILS ON
WHERE THIS BOUNDARY SETS UP REMAINS UNCERTAIN. THERE DOES SEEM TO BE
PRETTY GOOD CONSENSUS EVOLVING AMONG THE MODELS THAT THE HEAVY
MOUNTAIN RAIN WILL TAPER OFF FROM N TO S ON SUNDAY AND MOSTLY SHUT
OFF BY SUNDAY NIGHT AS THE RIDGE BEGINS TO BUILD.

.LONG TERM...THE EXTENDED FORECAST REMAINS CHALLENGING WITH A WIDE
RANGE OF SOLUTIONS AMONG THE MODELS. THERE IS SOME AGREEMENT THAT
MONDAY WILL GENERALLY FEATURE SHOWERS OR A LULL IN RAINFALL AS
HIGHER PRESSURE BUILDS ALOFT. MODELS DO NOT AGREE ON THE STRENGTH OR
TRACK OF THE NEXT SYSTEM APPROACHING FROM THE W ON TUESDAY. THE
LATEST 12/18Z GFS BRINGS THE LOW IN FURTHER N WHICH WOULD STILL
PRODUCE WARM ADVECTION RAINFALL ACROSS THE AREA...THOUGH NOT AS MUCH
AS WAS SHOWN BY PREVIOUS SOLUTIONS.

MOST MODELS DIG A COLD UPPER TROUGH SWD OUT OF B.C. THROUGH WRN WA
ON WEDNESDAY. THIS COULD USHER IN COOLER AIR BUT MODELS DISAGREE ON
THE EXTENT OF RIDGING OFFSHORE AND WHERE IT SETS UP. THE ECMWF
CONTINUES TO BE ONE OF THE COLDER SOLUTIONS AND HAS THE KONA LOW CUT
OFF FURTHER W...THUS A FURTHER W DEVELOPMENT OF THE UPPER RIDGE. THE
KONA LOW IS FURTHER E ON THE GFS40 WITH A RIDGE NEAR 135-140 WHICH
WILL STILL USHER IN COOLER NLY FLOW BUT PERHAPS LESS CHANCE OF
PRECIPITATION. IT WILL BE INTERESTING TO SEE HOW THIS PANS OUT BUT A
SWITCH TO COOLER OR COLD TEMPERATURES IS A POSSIBILITY BY THURSDAY.
POPS WERE TRIMMED WAY BACK AND MAY NEED TO BE REMOVED ALTOGETHER IF
MODEL TRENDS CONTINUE. SNOW LEVELS WILL ALSO BE MUCH
LOWER...POSSIBLY TO SEA LEVEL...BUT IT IS VERY UNCLEAR AS TO HOW
MUCH MOISTURE WILL REMAIN BY THAT TIME.

&&

.HYDROLOGY...THOUGH RAIN WILL FALL AT TIMES...FLOODING IS UNLIKELY
ON ANY RIVER THROUGH SATURDAY.

HEAVY RAIN COULD CAUSE FLOODING BY LATE THIS WEEKEND. A WEATHER
SYSTEM WITH STRONG WESTERLY FLOW ALOFT WILL BRING HEAVY RAIN AT
TIMES TO THE COAST AND OLYMPICS ON SATURDAY. HEAVY RAIN WILL SPREAD
INTO THE CASCADES SATURDAY AFTERNOON.

MODELS CURRENTLY TAPER RAIN OVER THE OLYMPICS ON SUNDAY BUT KEEP
HEAVY RAIN GOING IN THE CASCADES...ESPECIALLY OVER THE CASCADES FROM
ABOUT KING COUNTY SOUTH. THE TOTAL MODEL RAINFALL OVER ABOUT 48
HOURS FROM SATURDAY MORNING THROUGH SUNDAY NIGHT AMOUNTS TO AROUND
FOUR TO SIX INCHES OVER THE OLYMPICS AND CENTRAL CASCADES WITH A
TEN-INCH BULLSEYE OVER MOUNT RAINIER. THE SNOW LEVEL WILL BE ABOVE
5000 FEET ON SATURDAY AND SUNDAY BEFORE FALLING TO 3500 FEET OR SO
SUNDAY NIGHT.

THESE RAINFALL AMOUNTS ARE ENOUGH TO CAUSE FLOODING. AT THIS TIME
THE RIVERS MOST LIKELY TO FLOOD ARE THE ONES FLOWING OFF THE
CASCADES OF KING...PIERCE...AND LEWIS COUNTIES...AS WELL AS THE
UNUSUALLY FLOOD-PRONE SKOKOMISH RIVER IN MASON COUNTY. ANY FLOODING
WOULD LIKELY BEGIN AS EARLY AS SATURDAY NIGHT ON THE SKOKOMISH
RIVER. THE CASCADE RIVERS COULD FLOOD SUNDAY WITH CRESTS SUNDAY
NIGHT OR MONDAY.

A COOLER AND DRIER AIR MASS IS FORECAST TO BE OVER THE AREA NEXT
WEEK. AFTER MONDAY THE RIVERS WILL RECEDE AND ANY FURTHER FLOODING
IS UNLIKELY. BURKE

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY BEHIND THE FRONT.

AT 2230Z A STRONG FRONT WAS MOVING THROUGH THE OFFSHORE WATERS. IT
WILL PUSH ACROSS THE AREA REACHING THE INTERIOR VALLEYS ABOUT 08Z
FRIDAY THEN EAST OF THE CASCADES BY 12Z. LOW END VFR CONDITIONS THIS
AFTERNOON WILL DETERIORATE TO MVFR SHORTLY AFTER 00Z THIS EVENING AS
PRECIPITATION INCREASES WITH THE APPROACH OF THE FRONT.

THERE IS LIKELY TO BE A PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD AND ALONG THE COAST FOR A FEW
HOURS AHEAD OF THE FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40-50KT
AND SURFACE WINDS REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC035-040 WITH PERIODS OF LIGHT RAIN...WITH
CEILINGS DETERIORATING TO OVC015 BY 06Z. SE WIND 7-11 KT WILL SHIFT
TO S 11-17 KT WITH GUSTS TO 25 KT BEHIND THE FRONT 08Z-10Z. THERE
WILL BE 2-4 HOURS OF WIND 19035-40KT AT FL020 AHEAD OF THE INCOMING
FRONT ABOUT 05Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 970 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE WATERS TONIGHT. GALE FORCE WINDS CAN BE
EXPECTED OVER THE COASTAL WATERS AND AT THE EAST ENTRANCE TO THE
STRAIT UNTIL THE FRONT PASSES WITH SMALL CRAFT ADVISORY CONDITIONS
FOR THE STRAIT...NORTHERN INLAND WATERS...ADMIRALTY INLET AND PUGET
SOUND AND HOOD CANAL.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-25 FT SWELL THAT WILL REACH THE COAST
MIDDAY FRIDAY AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY. TIDAL
ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH
TIDE OCCURS SATURDAY MORNING. SOME COASTAL FLOODING IS POSSIBLE
ALONG THE COAST AROUND THE HIGH TIDE ON SATURDAY...AND A COASTAL
FLOOD WATCH IS IN EFFECT. A HIGH SURF ADVISORY WAS ISSUED FOR THE
COAST FROM MIDDAY FRIDAY THROUGH FRIDAY NIGHT.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. STRONG ONSHORE FLOW
SATURDAY NIGHT WILL SLOWLY DIMINISH ON SUNDAY. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
     WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
     4 PM PST THIS AFTERNOON THROUGH TONIGHT.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM LATE
     FRIDAY MORNING THROUGH EARLY SATURDAY MORNING.
     COASTAL FLOOD WATCH FOR THE NORTH AND CENTRAL COAST FROM
     SATURDAY MORNING THROUGH SATURDAY AFTERNOON.

PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST
     ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.
     GALE WATCH COAST...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...
     ADMIRALTY INLET...AND NORTHERN INLAND WATERS FRIDAY NIGHT
     THROUGH SATURDAY.




&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML

















000
FXUS66 KPQR 181816
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1016 AM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL INCREASE TONIGHT AS A MORE ORGANIZED FRONTAL
SYSTEM PUSHES ONSHORE. A COLDER UPPER TROUGH MOVES ACROSS THE AREA
FRIDAY...WHICH WILL LOWER SNOW LEVELS BELOW THE CASCADE PASSES. MILD
AND VERY WET WEATHER IS EXPECTED THIS WEEKEND. THERE IS POTENTIAL FOR
AN ATMOSPHERIC RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE
AREA. THE EXACT LOCATION OF THE JET STREAM AND ASSOCIATED MOISTURE
PLUME ARE STILL IN DOUBT. THERE IS THE POTENTIAL FOR SOME FLOODING
LATE THIS WEEKEND INTO EARLY NEXT WEEK.

&&

.UPDATE...SOME LIGHT RAIN CONTINUES TO SPREAD ACROSS SOUTHWEST
WASHINGTON AND NORTHWEST OREGON THIS MORNING AHEAD OF AN APPROACHING
FRONTAL SYSTEM. MODELS INDICATE THAT THIS RAIN WILL CONTINUE THROUGH
THE DAY WITH INCREASING COVERAGE...PARTICULARLY ALONG THE COAST AND
ACROSS THE NORTHERN PORTIONS OF THE FORECAST AREA. THEREFORE
INCREASED POPS FOR THESE LOCATIONS WITH THE MORNING UPDATE. EXPECT
THESE RAINFALL ACCUMULATIONS TO REMAIN FAIRLY LIGHT FOR MOST
LOCATIONS DURING THE DAY...THOUGH HEAVIER RAIN WILL MOVE ONSHORE WITH
THE COLD FRONT THIS EVENING. OTHERWISE...FEW CHANGES TO THE FORECAST.
12Z MODELS REMAIN CONSISTENT WITH SIGNIFICANT RAINFALL FOR THE
WEEKEND WITH A DEVELOPING ATMOSPHERIC RIVER EVENT.  CULLEN

&&

.PREV DISC... /ISSUED 414 AM PST THU DEC 18 2014/

SHORT TERM...THURSDAY THROUGH SATURDAY...WATER VAPOR IMAGERY AS OF
1030Z SHOWS A DEEP UPPER LOW IN THE GULF OF ALASKA WITH A FRONTAL
SYSTEM TAKING SHAPE NEAR 135W. THE 06Z NAM12 RUN SHOWS A WEAK SURFACE
LOW OFF THE S OREGON COAST AT 09Z. THIS FEATURE IS VERY DIFFICULT TO
PICK OUT IN THE WATER VAPOR LOOPER. THE NAM SHOWS THIS LOW FILLING
OVERNIGHT AS IT DRIFTS TO THE NE. NWS PORTLAND DUAL-POL DOPPLER RADAR
SHOWING DECREASING RADAR RETURNS...WITH THE STRONGEST ECHOES IN THE
WILLAPA HILLS AND S WA CASCADES.

NAM...GFS AND ECMWF ALL INDICATE A WEAK 500 MB RIDGE TO MOVE ACROSS
THE AREA TODAY. HOWEVER...MODEL CROSS-SECTIONS AND TIME-HEIGHT
FORECASTS MAINTAIN MOIST LOW-LEVELS THROUGH THE DAY. THUS...STILL
EXPECT LIGHT QPF ACROSS THE FORECAST AREA TODAY...AHEAD OF THE NEXT
FRONTAL SYSTEM. MODELS APPEAR TO BE IN REASONABLE AGREEMENT WITH THIS
FRONT...WITH LANDFALL SOMETIME AROUND 00Z FRI OR SHORTLY THEREAFTER.
ONE CONCERN WAS THE POTENTIAL FOR HIGH WIND ALONG THE COASTAL
HEADLANDS. PREVIOUS SHIFT HAD ISSUED A HIGH WIND WATCH FOR LATE THIS
AFTERNOON THROUGH 08Z FRI. UPON FURTHER REVIEW...NOT SEEING ENOUGH IN
THE 850 MB TO 950 MB WIND FIELDS TO UPGRADE TO A WARNING. THE 00Z
WRF-GFS VALID 00Z FRI HAS A COASTAL JET SIGNATURE OVER THE OREGON
COASTAL WATERS...WITH FORECAST 10M WIND GUSTS OF 55 KT. HOWEVER...BY
03Z FRI THE MODEL HAS JUST A SMALL SLIVER OF 55 KT GUSTS JUST OFF THE
CENTRAL COAST. WOULD NOT BE SURPRISED TO SEE ISOLATED 55 TO 60 MPH
GUSTS ON EXPOSED HEADLAND AREAS LATE THIS AFTERNOON THROUGH THE
MID-EVENING HOURS...BUT DO NOT THINK THESE WILL BE WIDESPREAD AND
FREQUENT ENOUGH TO WARRANT A WARNING.

THE SYSTEM WILL BRING A 6-9 HR SHOT OF RAIN TO THE AREA...BUT SNOW
LEVELS ARE EXPECTED TO SLOWLY RISE AHEAD OF THE FRONT. THE COLDER
UPPER TROUGH SLIDES ACROSS THE REGION FRI...WITH 1000-500 MB
THICKNESS VALUES DROPPING INTO THE LOW TO MID 530S BY 18Z FRI. THIS
PUTS SNOW LEVELS WELL BELOW THE CASCADE PASSES...BUT BY THIS TIME THE
BULK OF THE PRECIPITATION HAS ALREADY OCCURRED. ALTHOUGH NOT IN THE
FORECAST GRIDS AS OF YET...NEED TO CONSIDER THE POSSIBILITY OF
THUNDERSTORMS FOR FRI. GFS SOUNDING FOR KAST VALID 22Z FRI SHOWS LI
VALUES NEAR 0 BUT A SWEAT INDEX OF 272. THE 1000-750 MB LAPSE RATES
ARE AROUND 7.5C/KM.

MODELS STILL ADVERTISING A CHANGE TO A MUCH WETTER PATTERN STARTING
SAT. NAM AND GFS CONTINUE TO SHOW AN ATMOSPHERIC RIVER SET UP
DIRECTED AT SW WASHINGTON AND NW OREGON SAT. THE GEM MAY BE A BIT
SLOWER...BUT STILL HAS SUBSTANTIAL QPF DIRECTED AT THE FORECAST AREA
BY SAT NIGHT. THE 00Z WRFGFS SHOWS VERY HEAVY QPF WITH UP TO 8-12
INCHES OF RAIN IN THE HIGHER TERRAIN AND 2-4 INCHES IN THE WILLAMETTE
VALLEY SAT THROUGH MONDAY. WILL NEED TO MONITOR THIS VERY CLOSELY
OVER THE NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING
ON AREA MAINSTEM RIVERS.  WEISHAAR

LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN THE
MILD AND MOIST ATMOSPHERIC RIVER PATTERN THROUGH AT LEAST SUN. THE
ECMWF AND GEM GRADUALLY SHIFT THE FOCUS OF THE HEAVIEST PRECIP TO THE
N SUN AFTERNOON BUT THE GFS DOES NOT. EXPECT PLENTY OF RAINFALL TO
CONTINUE THROUGH SUNDAY. ON MONDAY AND TUESDAY...SOME WEAK RIDGING
MOVES OVER THE REGION BUT SHOWERS LIKELY CONTINUE IN THE MOIST
ONSHORE FLOW. THE ECMWF THEN INDICATES ANOTHER MAJOR PATTERN CHANGE
AROUND THE MIDDLE OF NEXT WEEK WITH A MUCH COLDER AIR MASS SETTLING
OVER THE PAC NW. HOWEVER...MOISTURE DIMINISHES DUE TO THE DRIER N-NE
FLOW. THUS...AFTER WHATEVER SNOW THE CASCADES GET LATE THIS WEEK...IT
WILL BE LOST OVER THE WEEKEND. THE GFS ALSO HAS A CHANGE TO COLDER
NW-N FLOW ALOFT BUT IT MAINTAINS AN OPEN TROUGH INSTEAD OF THE CLOSED
UPPER LOW ECMWF SOLUTION. WHILE STILL SOME SIGNIFICANT UNCERTAINTY
EXISTS WITH RESPECT TO THE TIMING OF THE COLD AIR AND JUST HOW COLD
THE AIR WILL BE...IT DOES APPEAR THAT A CHANGE TO MUCH COOLER
CONDITIONS WILL MOVE INTO THE REGION. SNOW LEVELS SHOULD BE QUITE LOW
OVER THE HOLIDAY...BUT DROPPED POPS SUBSTANTIALLY NEXT THU AND THU
NIGHT. WEISHAAR

&&

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

&&

.AVIATION...MIX OF VFR MVFR WILL CONTINUE THROUGH THE DAY TODAY AS
RAIN MOVES IN ACROSS THE AREA...BRINGING DOWN CIGS AND VIS. FRONT
MOVES ONSHORE AROUND 03Z...REACHING INLAND AROUND 05Z. THIS WILL
BRING PERIODS OF MVFR/IFR CIGS AND VIS WITH LIGHT TO MODERATE
RAIN. CIGS AND VIS TO STAY LOW MVFR/IFR THROUGH EARLY FRIDAY AS
CIGS WILL LIKELY LOWER BEHIND THE COLD FRONT.

KPDX AND APPROACHES...MVFR CIGS LIKELY TO PERSIST THROUGH THIS
MORNING AS RAIN MOVES THROUGH THE AREA. THERE MAY BE A PERIOD
WHERE CIGS LIFT TO VFR AFTER THIS INITIAL BAND...BUT CIGS SHOULD
DROP BACK TO MVFR WITH OCCASIONAL IFR AROUND 05Z AS THE FRONT
BRINGS RAIN THROUGH THE AREA. CIGS AND VIS SHOULD REMAIN MVFR/IFR
OVERNIGHT TONIGHT. -MCCOY

&&

.MARINE...COMBINED SEAS TO STAY AROUND 10 TO 12 FT...POSSIBLY
BUILDING TO NEAR 15 FT AROUND 1 PM TO 8 PM AS WINDS OUT OF THE SOUTH
REACH GALE FORCE WITH GUSTS OF 40 TO 45 KTS LIKELY. SEAS WILL START
TO SUBSIDE TO 10 TO 12 FT LATE THIS EVENING. A 20-22 FT SWELL TRAIN
WITH IMPRESSIVELY LONG PERIODS MOVES IN EARLY FRIDAY MORNING. MODELS
TEND TO UNDER-DO THE WAVE HEIGHTS IN THIS TYPE OF SCENARIO...SO WAVE
HEIGHTS MAY WELL BE UNDERDONE. AS OF NOW...EXPECT SEAS ON FRIDAY
MORNING NEARLY DOUBLE IN HEIGHT BY FRIDAY AFTERNOON. BECAUSE OF
THIS...A HIGH SURF ADVISORY WILL LIKELY BE ISSUED WITH OUR AFTERNOON
PACKAGE TODAY. THE GOOD NEWS IS THAT THE LARGEST SWELL WILL LIKELY
ARRIVE DURING LOW TIDE AND DURING THE NIGHT TIME HOURS WHEN MOST
MARINERS AND BEACH GOERS ARE NOT IN HARMS WAY.

ON SATURDAY MORNING ANOTHER FRONT MOVES THROUGH THE WATERS.
CONFIDENCE IS INCREASING FOR ANOTHER ROUND OF SOUTHERLY GALES...WITH
POSSIBLY SOME LOW END STORM FORCE GUSTS. THIS ON TOP OF THE 20 FT
SWELL SATURDAY COULD EASILY BRING SEAS UP INTO THE MIDDLE 20S LATE
SATURDAY MORNING INTO THE AFTERNOON. BEHIND THIS FRONT...SMALL
CRAFT WINDS OUT OF THE WEST-SOUTHWEST WILL CONTINUE THROUGH THE
DAY ON SUNDAY.

HIGH PRESSURE BUILDS IN EARLY NEXT WEEK BRINGING RELATIVELY BENIGN
WEATHER THROUGH MIDWEEK. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST FRIDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.



000
FXUS66 KOTX 181740
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
939 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
18Z TAFS: A saturated boundary layer north and west of KPUW will
result in widespread IFR/MVFR stratus over the Columbia Basin,
Spokane/Coeur D`Alene area extending north to the Canadian border
and west into the Cascade crest. The stratus should lift a bit
into the afternoon per forecast soundings. A drier boundary layer
over KPUW/KLWS will lead to continued VFR conditions. The next
weather system will spread -RA across the TAF sites overnight into
Friday morning with a mix of IFR and MVFR conditions.  JW

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 181740
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
939 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
18Z TAFS: A saturated boundary layer north and west of KPUW will
result in widespread IFR/MVFR stratus over the Columbia Basin,
Spokane/Coeur D`Alene area extending north to the Canadian border
and west into the Cascade crest. The stratus should lift a bit
into the afternoon per forecast soundings. A drier boundary layer
over KPUW/KLWS will lead to continued VFR conditions. The next
weather system will spread -RA across the TAF sites overnight into
Friday morning with a mix of IFR and MVFR conditions.  JW

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KSEW 181739 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
935 AM PST THU DEC 18 2014

UPDATED ADVISORIES.

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
      WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
      4 PM PST THIS AFTERNOON THROUGH TONIGHT.
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
      FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML















000
FXUS66 KSEW 181739 AAA
AFDSEW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SEATTLE WA
935 AM PST THU DEC 18 2014

UPDATED ADVISORIES.

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY THROUGH TONIGHT FOR THE SAN JUAN ISLANDS...
      WESTERN WHATCOM COUNTY...AND THE ADMIRALTY INLET AREA.
     WINTER WEATHER ADVISORY THROUGH TONIGHT FOR THE OLYMPICS.
     WINTER WEATHER ADVISORY FOR THE WEST SLOPES OF THE CASCADES
      4 PM PST THIS AFTERNOON THROUGH TONIGHT.
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
      FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML














000
FXUS66 KSEW 181712
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...DELAYED
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML












000
FXUS66 KSEW 181712
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...DELAYED
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML












000
FXUS66 KSEW 181712
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...DELAYED
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML












000
FXUS66 KSEW 181712
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...RADAR AND OBS INDICATE SHOWERS ACROSS MUCH OF WRN WA
THIS MORNING. ALTHOUGH A WEAK UPPER RIDGE IS TRAVERSING THE AREA
TODAY...THE FLOW REMAINS MOIST AND SLY. BUFFER SOUNDS SHOW THE AIR
MASS BELOW 750 MB TO BE WEAKLY UNSTABLE THROUGH MIDDAY SO SHOWERS
WILL CONTINUE THROUGH THE MORNING AND PROBABLY UP THE POINT WHEN
WARM ADVECTION RAIN BEGINS.

IR SATELLITE IMAGERY AND THE COASTAL RADAR SHOW MORE STEADY RAIN
APPROACHING THE COAST. THIS WILL SPREAD INLAND LATE IN THE DAY.
BRIGHTER CLOUD TOPS APPEAR TO INDICATE SOME SPLITTING ALREADY
OCCURING WITH THE FRONT. A STRONGER PORTION IS MOVING E-NE INTO
B.C./WA AND ANOTHER PORTION PUSHING DUE E INTO OREGON. MODELS
INDICATE THE FRONT HOLDS TOGETHER ENOUGH TO PRODUCE MORE WIDESPREAD
RAINFALL THAN PAST SYSTEMS THIS WEEK BUT IT WILL BE IN A WEAKENING
STATE AS IT ARRIVES LATER TODAY/EARLY THIS EVENING.

QPF AMOUNTS ON VARIOUS MESO MODELS GENERALLY AVERAGE A HALF TO ONE
INCH LIQUID IN 12 HOURS FROM 00Z-12Z TONIGHT OVER THE MOUNTAINS.
AREAS THAT PREDOMINATELY REMAIN AS SNOW THROUGH THE EVENT COULD SEE
UP TO A FOOT OF SNOW. SNOW LEVELS ARE THE TRICKY PART OF THE
FORECAST AS CURRENT PASS TEMPERATURES ARE IN THE UPPER 20S WITH ELY
GRADIENT WHICH MAY KEEP SOME PASSES COLD FOR SOME TIME THIS EVENING.
THE MAIN SNOW LEVEL IS CURRENTLY NEAR 3500 FEET BASED ON THE KUIL
FREEZING LEVELS MINUS 1K FT. THIS WILL CLIMB AS WARM ADVECTION
PRECIPITATION OVERSPREADS THE AREA BY LATE TODAY OR THIS EVENING.
WILL GO AHEAD AND ISSUE A SNOW ADVISORY FOR 5 TO 10 INCH SNOW
AMOUNTS BUT STRESSING THE LOWER END AMOUNTS WILL FALL AT HIGHER
PASSES SUCH AS WHITE PASS AND STEVENS PASS ASSUMING SOME CHANGE OVER
TO RAIN OR FREEZING RAIN AS THE FRONT PUSHES ACROSS LATER TONIGHT.
SNOQUALMIE PASS WILL LIKELY SEE SNOW CHANGE OVER TO RAIN PRETTY
QUICKLY WITH LESS THAN A COUPLE INCHES THERE. THE FRONT WILL
ACTUALLY HELP TO MIX THE COLDER AIR OUT OF THE PASSES AND RAISE SNOW
LEVELS THERE. HOWEVER...THE MAIN FREE AIR SNOW LEVELS WILL FALL BACK
TO AROUND 3000 FEET FRIDAY MORNING AFTER LIFTING TO 4500-5000 FEET
TONIGHT. SKI RESORTS EXPOSED TO S/SW FLOW SUCH AS MOUNT BAKER AND
PARADISE SHOULD DO BEST IN THIS FLOW PATTERN IF THEY REMAIN AS ALL
SNOW WITH UP TO 10 INCHES IN THESE AREAS.

LASTLY...WINDY CONDITIONS ARE EXPECTED TO DEVELOP UP N LATER THIS
AFTERNOON THROUGH THIS EVENING. SE GRADIENTS TIGHTEN AND A MESO LOW
WILL LIKELY FORM AROUND PORT ANGELES/SEQUIM.  THIS SHOULD INDUCE
LOCALLY STRONGER SE WINDS W/ GUSTS TO 45 MPH ACROSS ADMIRALTY
INLET...THE SAN JUANS...AND EXPOSED LOCATIONS ALONG THE SHORES OF
WRN WHATCOM COUNTY. BOTH THE HRRR/NAM12 SHOW LOW END ADVISORY WINDS
AND WILL PLAN TO ISSUE AN ADVISORY THIS MORNING FOR THE LATE
AFTERNOON AND EVENING HOURS.

A MOIST ONSHORE POST-FRONTAL PATTERN DEVELOPS FRIDAY WITH WEAK
INSTABILITY IN THE LOWER LEVELS. THIS SHOULD TRANSLATE TO SHOWERS
FOR OUR AREA UNTIL THE NEXT SYSTEM ARRIVES. LATEST 06Z/12Z MODELS
BRING WARM ADVECTION RAIN TO THE COAST LATE FRIDAY NIGHT...THEN
OVERSPREADING THE ENTIRE AREA BY THE MID MORNING HOURS ON SATURDAY.
MODELS CONTINUE TO SHOW A LOT OF FLOW SO RAINFALL RATES WILL BE
HEAVY ALONG THE S/SW FACING SLOPES OF THE MOUNTAINS...ESPECIALLY THE
OLYMPICS. A TRAILING MOISTURE PLUM WILL BECOME DIRECTED AT WRN WA BY
SATURDAY EVENING AS THE FLOW TURNS MORE WLY. THIS WILL GENERATE
ADDITIONAL OROGRAPHICALLY ENHANCED RAIN ALONG THE W/SW SLOPES OF THE
OLYMPICS/CASCADES SATURDAY NIGHT INTO EARLY SUNDAY. THIS COULD CAUSE
SOME MINOR FLOODING ON PRONE RIVERS...SEE THE LATEST HYDRO
DISCUSSION BELOW FOR DETAILS. SE GRADIENTS WILL ALSO BE QUITE STRONG
WITH THE WARM FRONT. AREAS FROM ADMIRALTY INLET NWD WILL LIKELY NEED
A WIND ADVISORY AND POSSIBLY THE COAST. MERCER

.LONG TERM...NO UPDATE FROM PREVIOUS DISCUSSION...ECMWF AND GFS SHOW
STRONG ZONAL FLOW CONTINUING INTO EARLY NEXT WEEK WITH A BROAD FLAT
UPPER LEVEL RIDGE OVER THE REGION. LOTS OF FLOW THROUGH THE RIDGE
WILL KEEP THIS A GENERALLY WET AND BREEZY PERIOD THROUGH SUNDAY. THE
MAIN PROBLEM WILL REMAIN HEAVY RAIN SATURDAY NIGHT. FAIRLY STRONG
WESTERLY 850 MB FLOW WILL REMAIN 30-45KT SATURDAY NIGHT INTO SUNDAY
MORNING...THEN GRADUALLY DIMINISH OVER THE NORTH AND CENTRAL PART OF
W WA SUNDAY AFTERNOON. STRONGER W FLOW WILL CONTINUE OVER NW OREGON
AND THE SOUTHERN WA CASCADES. THERE COULD BE ANOTHER 2-3 INCHES OF
QPF OVER THE CENTRAL CASCADES 12Z SUNDAY THROUGH 12Z MONDAY WHICH
COULD BRING SOME CASCADE RIVERS CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...NO UPDATE FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH FRIDAY NIGHT. A MOIST WESTERLY FLOW PATTERN
WILL DEVELOP SATURDAY AND CONTINUE THROUGH SUNDAY NIGHT WITH HEAVY
RAIN AT TIMES IN THE MOUNTAINS. A STRONG WARM FRONT WILL CROSS THE
AREA SATURDAY WITH STRONG S FLOW OVER THE OLYMPICS BECOMING W BY
LATE AFTERNOON. THE STRONG W FLOW WILL REACH THE CASCADES SATURDAY
NIGHT. 2-3 INCHES OF RAIN ARE EXPECTED OVER THE OLYMPICS AND PARTS
OF THE CASCADES DURING THE 24 HOUR PERIOD FROM 12Z SATURDAY THROUGH
12Z SUNDAY. THIS COULD CAUSE ANOTHER ROUND OF FLOODING ON THE
SKOKOMISH RIVER AND PRIME SOME OF THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A STRONG PACIFIC FRONTAL SYSTEM OVER THE OFFSHORE WATERS
WILL MOVE ACROSS THE AREA TONIGHT. SOUTHWESTERLY FLOW ALOFT WILL
INCREASE AND BECOMING STRONG THIS EVENING THEN BECOMING MODERATE ON
FRIDAY. THE AIR MASS IS MOIST AND STABLE...IT WILL BECOME SOMEWHAT
UNSTABLE LATE TONIGHT AND FRIDAY.

AT 1630Z A STRONG FRONT AROUND 130W IS MOVING EAST. IT WILL PUSH
ACROSS THE AREA REACHING THE INTERIOR VALLEYS JUST AFTER 08Z FRIDAY
THEN EAST OF THE CASCADES BY 12Z. PRESSURE GRADIENTS ARE
INCREASINGLY SOUTHEASTERLY IN ADVANCE OF THE FRONT...SO DESPITE RAIN
BANDS OFFSHORE MOVING INLAND...CEILINGS WILL BECOME PREDOMINATELY
VFR. EXPECT CEILINGS AND VISIBILITIES TO DETERIORATE TO MVFR ALONG
THE COAST MIDDAY AND IN THE INTERIOR SHORTLY AFTER 00Z THIS EVENING
AS PRECIPITATION DEVELOPS AND GRADUALLY INCREASES WITH THE APPROACH
OF THE FRONT.

THERE COULD BE A SHORT PERIOD OF LOW LEVEL WIND SHEAR IN THE
INTERIOR FROM ABOUT KPAE SOUTHWARD FOR A FEW HOURS AHEAD OF THE
FRONT AS WINDS AT 2000 FT INCREASE TO SSW 40KT AND SURFACE WINDS
REMAIN SELY.

POST FRONTAL ONSHORE FLOW WITH SCATTERED SHOWERS ARE EXPECTED BEHIND
THE FRONT LATE TONIGHT AND FRIDAY WITH MVFR CONDITIONS AND SOME
CLEARING AT TIMES IN THE LEE OF THE OLYMPICS. ISOLATED THUNDERSTORMS
ARE NOT OUT OF THE QUESTION ALONG THE COAST ON FRIDAY AS COLD AIR
ALOFT ARRIVES WITH AN UPPER LEVEL TROUGH. ALBRECHT

KSEA...EXPECT BKN-OVC040-050 TODAY. PERIODS OF -RA WILL DEVELOP THIS
AFTERNOON. CEILINGS WILL GRADUALLY LOWER TO MVFR THIS EVENING WITH
CIGS BOTTOMING OUT AROUND 015 A COUPLE HOURS AHEAD OF FRONTAL
PASSAGE 08Z-10Z FRIDAY. EXPECT SE WIND 5 KT TO INCREASE TO 9-11 KT
THIS EVENING THEN SHIFT TO S 10-14 KT BEHIND THE FRONT 08Z-10Z.
THERE WILL BE A COUPLE HOURS OF WIND 18035-40KT AT FL020 AHEAD OF
THE INCOMING FRONT ABOUT 06Z-08Z TIME PERIOD. ALBRECHT

&&

.MARINE...A FRONT ASSOCIATED WITH A 968 MB LOW WELL WEST OF HAIDA
GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN INLAND
TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS BEGINNING MIDDAY TODAY THROUGH THIS EVENING WITH
SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. GALE FORCE WINDS ARE NOW EXPECTED AT
THE EAST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THIS AFTERNOON AND
TONIGHT AS A MESOSCALE LOW DEVELOPS TO THE NORTHEAST OF THE
OLYMPICS.

EXPECT MODERATE TO STRONG ONSHORE FLOW BEHIND THE FRONT AND WITH A
SURFACE TROUGH AS IT MOVES ACROSS THE AREA ON FRIDAY. SMALL CRAFT
ADVISORY CONDITIONS WILL CONTINUE OVER THE COASTAL WATERS AND
POSSIBLY SOME OF THE INTERIOR ZONES. ISOLATED THUNDERSTORMS CANNOT
BE RULED OUT OVER THE COASTAL WATERS ON FRIDAY IN A RATHER UNSTABLE
AIR MASS.

30-45 FOOT WAVES OVER A LARGE AREA OF THE NORTH CENTRAL PACIFIC WILL
DECAY TO A LONG PERIOD 22-23 FT SWELL THAT WILL REACH THE COAST
FRIDAY AFTERNOON AND CONTINUE TO PUSH ONSHORE THROUGH SATURDAY.
TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FOOT ABOVE NORMAL
AND HIGH TIDE OCCURS SATURDAY MORNING. IF SWELL REMAINS HIGH INTO
SATURDAY MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE. A COASTAL FLOOD WATCH MAY BE REQUIRED FOR PORTIONS OF THE
COAST FOR THE SATURDAY MORNING HIGH TIDE.

ANOTHER STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE
FORCE WINDS ONCE AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN
INLAND WATERS...AND THE STRAIT ENTRANCES. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...DELAYED
PZ...GALE WARNING THROUGH TONIGHT COASTAL WATERS AND EAST ENTRANCE.
     SMALL CRAFT ADVISORY ALL REMAINING WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR TONIGHT THROUGH
     FRIDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML












000
FXUS66 KPQR 181216
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
414 AM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL REDEVELOP BY LATE THIS AFTERNOON AND INCREASE
THURSDAY NIGHT AS A MORE ORGANIZED FRONTAL SYSTEM MOVES ONSHORE. A
COLDER UPPER TROUGH MOVES ACROSS THE AREA FRIDAY...WHICH WILL LOWER
SNOW LEVLES BELOW THE CASCADE PASSES. MILD AND VERY WET WEATHER IS
EXPECTED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC RIVER
AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA. THE EXACT
LOCATION OF THE JET STREAM AND ASSOCIATED MOISTURE PLUME ARE STILL IN
DOUBT. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...WATER VAPOR IMAGERY AS OF
1030Z SHOWS A DEEP UPPER LOW IN THE GULF OF ALASKA WITH A FRONTAL
SYSTEM TAKING SHAPE NEAR 135W. THE 06Z NAM12 RUN SHOWS A WEAK SURFACE
LOW OFF THE S OREGON COAST AT 09Z. THIS FEATURE IS VERY DIFFICULT TO
PICK OUT IN THE WATER VAPOR LOOPER. THE NAM SHOWS THIS LOW FILLING
OVERNIGHT AS IT DRIFTS TO THE NE. NWS PORTLAND DUAL-POL DOPPLER RADAR
SHOWING DECREASING RADAR RETURNS...WITH THE STRONGEST ECHOES IN THE
WILLAPA HILLS AND S WA CASCADES.

NAM...GFS AND ECMWF ALL INDICATE A WEAK 500 MB RIDGE TO MOVE ACROSS
THE AREA TODAY. HOWEVER...MODEL CROSS-SECTIONS AND TIME-HEIGHT
FORECASTS MAINTAIN MOIST LOW-LEVELS THROUGH THE DAY. THUS...STILL
EXPECT LIGHT QPF ACROSS THE FORECAST AREA TODAY...AHEAD OF THE NEXT
FRONTAL SYSTEM. MODELS APPEAR TO BE IN REASONABLE AGREEMENT WITH THIS
FRONT...WITH LANDFALL SOMETIME AROUND 00Z FRI OR SHORTLY THEREAFTER.
ONE CONCERN WAS THE POTENTIAL FOR HIGH WIND ALONG THE COASTAL
HEADLANDS. PREVIOUS SHIFT HAD ISSUED A HIGH WIND WATCH FOR LATE THIS
AFTERNOON THROUGH 08Z FRI. UPON FURTHER REVIEW...NOT SEEING ENOUGH IN
THE 850 MB TO 950 MB WIND FIELDS TO UPGRADE TO A WARNING. THE 00Z
WRF-GFS VALID 00Z FRI HAS A COASTAL JET SIGNATURE OVER THE OREGON
COASTAL WATERS...WITH FORECAST 10M WIND GUSTS OF 55 KT. HOWEVER...BY
03Z FRI THE MODEL HAS JUST A SMALL SLIVER OF 55 KT GUSTS JUST OFF THE
CENTRAL COAST. WOULD NOT BE SURPRISED TO SEE ISOLATED 55 TO 60 MPH
GUSTS ON EXPOSED HEADLAND AREAS LATE THIS AFTERNOON THROUGH THE
MID-EVENING HOURS...BUT DO NOT THINK THESE WILL BE WIDESPREAD AND
FREQUENT ENOUGH TO WARRANT A WARNING.

THE SYSTEM WILL BRING A 6-9 HR SHOT OF RAIN TO THE AREA...BUT SNOW
LEVELS ARE EXPECTED TO SLOWLY RISE AHEAD OF THE FRONT. THE COLDER
UPPER TROUGH SLIDES ACROSS THE REGION FRI...WITH 1000-500 MB
THICKNESS VALUES DROPPING INTO THE LOW TO MID 530S BY 18Z FRI. THIS
PUTS SNOW LEVELS WELL BELOW THE CASCADE PASSES...BUT BY THIS TIME THE
BULK OF THE PRECIPITATION HAS ALREADY OCCURRED. ALTHOUGH NOT IN THE
FORECAST GRIDS AS OF YET...NEED TO CONSIDER THE POSSIBILITY OF
THUNDERSTORMS FOR FRI. GFS SOUNDING FOR KAST VALID 22Z FRI SHOWS LI
VALUES NEAR 0 BUT A SWEAT INDEX OF 272. THE 1000-750 MB LAPSE RATES
ARE AROUND 7.5C/KM.

MODELS STILL ADVERTISING A CHANGE TO A MUCH WETTER PATTERN STARTING
SAT. NAM AND GFS CONTINUE TO SHOW AN ATMOSPHERIC RIVER SET UP
DIRECTED AT SW WASHINGTON AND NW OREGON SAT. THE GEM MAY BE A BIT
SLOWER...BUT STILL HAS SUBSTANTIAL QPF DIRECTED AT THE FORECAST AREA
BY SAT NIGHT. THE 00Z WRFGFS SHOWS VERY HEAVY QPF WITH UP TO 8-12
INCHES OF RAIN IN THE HIGHER TERRAIN AND 2-4 INCHES IN THE WILLAMETTE
VALLEY SAT THROUGH MONDAY. WILL NEED TO MONITOR THIS VERY CLOSELY
OVER THE NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING
ON AREA MAINSTEM RIVERS.  WEISHAAR

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN THE
MILD AND MOIST ATMOSPHERIC RIVER PATTERN THROUGH AT LEAST SUN. THE
ECMWF AND GEM GRADUALLY SHIFT THE FOCUS OF THE HEAVIEST PRECIP TO THE
N SUN AFTERNOON BUT THE GFS DOES NOT. EXPECT PLENTY OF RAINFALL TO
CONTINUE THROUGH SUNDAY. ON MONDAY AND TUESDAY...SOME WEAK RIDGING
MOVES OVER THE REGION BUT SHOWERS LIKELY CONTINUE IN THE MOIST
ONSHORE FLOW. THE ECMWF THEN INDICATES ANOTHER MAJOR PATTERN CHANGE
AROUND THE MIDDLE OF NEXT WEEK WITH A MUCH COLDER AIR MASS SETTLING
OVER THE PAC NW. HOWEVER...MOISTURE DIMINISHES DUE TO THE DRIER N-NE
FLOW. THUS...AFTER WHATEVER SNOW THE CASCADES GET LATE THIS WEEK...IT
WILL BE LOST OVER THE WEEKEND. THE GFS ALSO HAS A CHANGE TO COLDER
NW-N FLOW ALOFT BUT IT MAINTAINS AN OPEN TROUGH INSTEAD OF THE CLOSED
UPPER LOW ECMWF SOLUTION. WHILE STILL SOME SIGNIFICANT UNCERTAINTY
EXISTS WITH RESPECT TO THE TIMING OF THE COLD AIR AND JUST HOW COLD
THE AIR WILL BE...IT DOES APPEAR THAT A CHANGE TO MUCH COOLER
CONDITIONS WILL MOVE INTO THE REGION. SNOW LEVELS SHOULD BE QUITE LOW
OVER THE HOLIDAY...BUT DROPPED POPS SUBSTANTIALLY NEXT THU AND THU
NIGHT. WEISHAAR

&&

.AVIATION...LIGHT WINDS AND A MOIST LOWER ATMOSPHERE WILL CONTINUE
TO BRING A MIX OF IFR TO VFR CONDITIONS THROUGH LATE THURSDAY
MORNING. AS THE NEXT FRONT APPROACHES AND THE WINDS PICK UP AHEAD
OF IT EXPECT MOST TAF SITES TO IMPROVE TO VFR BY THURSDAY
AFTERNOON. THE FRONT WILL LIKELY PUSH INTO THE COAST AROUND 03Z
FRIDAY...AND INTO THE INTERIOR AROUND 06Z FRIDAY. EXPECT BRIEF
PERIODS OF IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS ASSOCIATED WITH THE FRONT.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PERSIST THROUGH
FRIDAY MORNING. HOWEVER...BRIEF PERIODS OF MVFR CIGS ARE POSSIBLE
THROUGH LATE THURSDAY MORNING DUE TO A MOIST LOWER ATMOSPHERE. A
FRONT WILL PUSH THROUGH AFTER 06Z FRIDAY AND COULD BRING BRIEF
PERIODS TO IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS. /64

&&

.MARINE...SEAS CONTINUED TO HOVER AROUND 10 FT OVERNIGHT AND LOOKS
TO REMAIN ELEVATED THROUGHOUT THE MORNING SO THE SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED TO 1 PM. A STRONG
FRONTAL SYSTEM IS STILL ON TRACK TO MOVE ACROSS THE WATERS TODAY
AND WILL BRING SOLID GALE GUSTS THROUGH THURSDAY NIGHT WITH SEAS
CLIMBING INTO THE MID TEENS. /64

PREVIOUS DISCUSSION FOLLOWS...EXPECT SEAS TO SUBSIDE FAIRLY
QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE THURSDAY NIGHT
INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER WAVE HEIGHTS WILL
BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD WESTERLY SWELL WILL
LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY EVENING. WAVE HEIGHTS
MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS COULD CERTAINLY CATCH
OFF GUARD ANY UNINFORMED MARINERS THAT VENTURE OUT FRIDAY MORNING.
CONFIDENCE IS RELATIVELY HIGH THAT THIS SWELL WILL LIKELY EXCEED
20 FT. IN FACT...THESE PATTERNS OFTEN PRODUCE HIGHER SEAS THAN
FORECASTED BY THE ENP WAVE MODEL. A HIGH SURF ADVISORY APPEARS
LIKELY. THE GOOD NEWS IS THAT THE LARGEST SWELL WILL LIKELY ARRIVE
DURING LOW TIDE AND DURING THE NIGHT TIME HOURS WHEN MOST MARINERS
AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST FRIDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 181216
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
414 AM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL REDEVELOP BY LATE THIS AFTERNOON AND INCREASE
THURSDAY NIGHT AS A MORE ORGANIZED FRONTAL SYSTEM MOVES ONSHORE. A
COLDER UPPER TROUGH MOVES ACROSS THE AREA FRIDAY...WHICH WILL LOWER
SNOW LEVLES BELOW THE CASCADE PASSES. MILD AND VERY WET WEATHER IS
EXPECTED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC RIVER
AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA. THE EXACT
LOCATION OF THE JET STREAM AND ASSOCIATED MOISTURE PLUME ARE STILL IN
DOUBT. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...WATER VAPOR IMAGERY AS OF
1030Z SHOWS A DEEP UPPER LOW IN THE GULF OF ALASKA WITH A FRONTAL
SYSTEM TAKING SHAPE NEAR 135W. THE 06Z NAM12 RUN SHOWS A WEAK SURFACE
LOW OFF THE S OREGON COAST AT 09Z. THIS FEATURE IS VERY DIFFICULT TO
PICK OUT IN THE WATER VAPOR LOOPER. THE NAM SHOWS THIS LOW FILLING
OVERNIGHT AS IT DRIFTS TO THE NE. NWS PORTLAND DUAL-POL DOPPLER RADAR
SHOWING DECREASING RADAR RETURNS...WITH THE STRONGEST ECHOES IN THE
WILLAPA HILLS AND S WA CASCADES.

NAM...GFS AND ECMWF ALL INDICATE A WEAK 500 MB RIDGE TO MOVE ACROSS
THE AREA TODAY. HOWEVER...MODEL CROSS-SECTIONS AND TIME-HEIGHT
FORECASTS MAINTAIN MOIST LOW-LEVELS THROUGH THE DAY. THUS...STILL
EXPECT LIGHT QPF ACROSS THE FORECAST AREA TODAY...AHEAD OF THE NEXT
FRONTAL SYSTEM. MODELS APPEAR TO BE IN REASONABLE AGREEMENT WITH THIS
FRONT...WITH LANDFALL SOMETIME AROUND 00Z FRI OR SHORTLY THEREAFTER.
ONE CONCERN WAS THE POTENTIAL FOR HIGH WIND ALONG THE COASTAL
HEADLANDS. PREVIOUS SHIFT HAD ISSUED A HIGH WIND WATCH FOR LATE THIS
AFTERNOON THROUGH 08Z FRI. UPON FURTHER REVIEW...NOT SEEING ENOUGH IN
THE 850 MB TO 950 MB WIND FIELDS TO UPGRADE TO A WARNING. THE 00Z
WRF-GFS VALID 00Z FRI HAS A COASTAL JET SIGNATURE OVER THE OREGON
COASTAL WATERS...WITH FORECAST 10M WIND GUSTS OF 55 KT. HOWEVER...BY
03Z FRI THE MODEL HAS JUST A SMALL SLIVER OF 55 KT GUSTS JUST OFF THE
CENTRAL COAST. WOULD NOT BE SURPRISED TO SEE ISOLATED 55 TO 60 MPH
GUSTS ON EXPOSED HEADLAND AREAS LATE THIS AFTERNOON THROUGH THE
MID-EVENING HOURS...BUT DO NOT THINK THESE WILL BE WIDESPREAD AND
FREQUENT ENOUGH TO WARRANT A WARNING.

THE SYSTEM WILL BRING A 6-9 HR SHOT OF RAIN TO THE AREA...BUT SNOW
LEVELS ARE EXPECTED TO SLOWLY RISE AHEAD OF THE FRONT. THE COLDER
UPPER TROUGH SLIDES ACROSS THE REGION FRI...WITH 1000-500 MB
THICKNESS VALUES DROPPING INTO THE LOW TO MID 530S BY 18Z FRI. THIS
PUTS SNOW LEVELS WELL BELOW THE CASCADE PASSES...BUT BY THIS TIME THE
BULK OF THE PRECIPITATION HAS ALREADY OCCURRED. ALTHOUGH NOT IN THE
FORECAST GRIDS AS OF YET...NEED TO CONSIDER THE POSSIBILITY OF
THUNDERSTORMS FOR FRI. GFS SOUNDING FOR KAST VALID 22Z FRI SHOWS LI
VALUES NEAR 0 BUT A SWEAT INDEX OF 272. THE 1000-750 MB LAPSE RATES
ARE AROUND 7.5C/KM.

MODELS STILL ADVERTISING A CHANGE TO A MUCH WETTER PATTERN STARTING
SAT. NAM AND GFS CONTINUE TO SHOW AN ATMOSPHERIC RIVER SET UP
DIRECTED AT SW WASHINGTON AND NW OREGON SAT. THE GEM MAY BE A BIT
SLOWER...BUT STILL HAS SUBSTANTIAL QPF DIRECTED AT THE FORECAST AREA
BY SAT NIGHT. THE 00Z WRFGFS SHOWS VERY HEAVY QPF WITH UP TO 8-12
INCHES OF RAIN IN THE HIGHER TERRAIN AND 2-4 INCHES IN THE WILLAMETTE
VALLEY SAT THROUGH MONDAY. WILL NEED TO MONITOR THIS VERY CLOSELY
OVER THE NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING
ON AREA MAINSTEM RIVERS.  WEISHAAR

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN THE
MILD AND MOIST ATMOSPHERIC RIVER PATTERN THROUGH AT LEAST SUN. THE
ECMWF AND GEM GRADUALLY SHIFT THE FOCUS OF THE HEAVIEST PRECIP TO THE
N SUN AFTERNOON BUT THE GFS DOES NOT. EXPECT PLENTY OF RAINFALL TO
CONTINUE THROUGH SUNDAY. ON MONDAY AND TUESDAY...SOME WEAK RIDGING
MOVES OVER THE REGION BUT SHOWERS LIKELY CONTINUE IN THE MOIST
ONSHORE FLOW. THE ECMWF THEN INDICATES ANOTHER MAJOR PATTERN CHANGE
AROUND THE MIDDLE OF NEXT WEEK WITH A MUCH COLDER AIR MASS SETTLING
OVER THE PAC NW. HOWEVER...MOISTURE DIMINISHES DUE TO THE DRIER N-NE
FLOW. THUS...AFTER WHATEVER SNOW THE CASCADES GET LATE THIS WEEK...IT
WILL BE LOST OVER THE WEEKEND. THE GFS ALSO HAS A CHANGE TO COLDER
NW-N FLOW ALOFT BUT IT MAINTAINS AN OPEN TROUGH INSTEAD OF THE CLOSED
UPPER LOW ECMWF SOLUTION. WHILE STILL SOME SIGNIFICANT UNCERTAINTY
EXISTS WITH RESPECT TO THE TIMING OF THE COLD AIR AND JUST HOW COLD
THE AIR WILL BE...IT DOES APPEAR THAT A CHANGE TO MUCH COOLER
CONDITIONS WILL MOVE INTO THE REGION. SNOW LEVELS SHOULD BE QUITE LOW
OVER THE HOLIDAY...BUT DROPPED POPS SUBSTANTIALLY NEXT THU AND THU
NIGHT. WEISHAAR

&&

.AVIATION...LIGHT WINDS AND A MOIST LOWER ATMOSPHERE WILL CONTINUE
TO BRING A MIX OF IFR TO VFR CONDITIONS THROUGH LATE THURSDAY
MORNING. AS THE NEXT FRONT APPROACHES AND THE WINDS PICK UP AHEAD
OF IT EXPECT MOST TAF SITES TO IMPROVE TO VFR BY THURSDAY
AFTERNOON. THE FRONT WILL LIKELY PUSH INTO THE COAST AROUND 03Z
FRIDAY...AND INTO THE INTERIOR AROUND 06Z FRIDAY. EXPECT BRIEF
PERIODS OF IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS ASSOCIATED WITH THE FRONT.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PERSIST THROUGH
FRIDAY MORNING. HOWEVER...BRIEF PERIODS OF MVFR CIGS ARE POSSIBLE
THROUGH LATE THURSDAY MORNING DUE TO A MOIST LOWER ATMOSPHERE. A
FRONT WILL PUSH THROUGH AFTER 06Z FRIDAY AND COULD BRING BRIEF
PERIODS TO IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS. /64

&&

.MARINE...SEAS CONTINUED TO HOVER AROUND 10 FT OVERNIGHT AND LOOKS
TO REMAIN ELEVATED THROUGHOUT THE MORNING SO THE SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED TO 1 PM. A STRONG
FRONTAL SYSTEM IS STILL ON TRACK TO MOVE ACROSS THE WATERS TODAY
AND WILL BRING SOLID GALE GUSTS THROUGH THURSDAY NIGHT WITH SEAS
CLIMBING INTO THE MID TEENS. /64

PREVIOUS DISCUSSION FOLLOWS...EXPECT SEAS TO SUBSIDE FAIRLY
QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE THURSDAY NIGHT
INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER WAVE HEIGHTS WILL
BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD WESTERLY SWELL WILL
LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY EVENING. WAVE HEIGHTS
MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS COULD CERTAINLY CATCH
OFF GUARD ANY UNINFORMED MARINERS THAT VENTURE OUT FRIDAY MORNING.
CONFIDENCE IS RELATIVELY HIGH THAT THIS SWELL WILL LIKELY EXCEED
20 FT. IN FACT...THESE PATTERNS OFTEN PRODUCE HIGHER SEAS THAN
FORECASTED BY THE ENP WAVE MODEL. A HIGH SURF ADVISORY APPEARS
LIKELY. THE GOOD NEWS IS THAT THE LARGEST SWELL WILL LIKELY ARRIVE
DURING LOW TIDE AND DURING THE NIGHT TIME HOURS WHEN MOST MARINERS
AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST FRIDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 181216
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
414 AM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL REDEVELOP BY LATE THIS AFTERNOON AND INCREASE
THURSDAY NIGHT AS A MORE ORGANIZED FRONTAL SYSTEM MOVES ONSHORE. A
COLDER UPPER TROUGH MOVES ACROSS THE AREA FRIDAY...WHICH WILL LOWER
SNOW LEVLES BELOW THE CASCADE PASSES. MILD AND VERY WET WEATHER IS
EXPECTED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC RIVER
AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA. THE EXACT
LOCATION OF THE JET STREAM AND ASSOCIATED MOISTURE PLUME ARE STILL IN
DOUBT. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...WATER VAPOR IMAGERY AS OF
1030Z SHOWS A DEEP UPPER LOW IN THE GULF OF ALASKA WITH A FRONTAL
SYSTEM TAKING SHAPE NEAR 135W. THE 06Z NAM12 RUN SHOWS A WEAK SURFACE
LOW OFF THE S OREGON COAST AT 09Z. THIS FEATURE IS VERY DIFFICULT TO
PICK OUT IN THE WATER VAPOR LOOPER. THE NAM SHOWS THIS LOW FILLING
OVERNIGHT AS IT DRIFTS TO THE NE. NWS PORTLAND DUAL-POL DOPPLER RADAR
SHOWING DECREASING RADAR RETURNS...WITH THE STRONGEST ECHOES IN THE
WILLAPA HILLS AND S WA CASCADES.

NAM...GFS AND ECMWF ALL INDICATE A WEAK 500 MB RIDGE TO MOVE ACROSS
THE AREA TODAY. HOWEVER...MODEL CROSS-SECTIONS AND TIME-HEIGHT
FORECASTS MAINTAIN MOIST LOW-LEVELS THROUGH THE DAY. THUS...STILL
EXPECT LIGHT QPF ACROSS THE FORECAST AREA TODAY...AHEAD OF THE NEXT
FRONTAL SYSTEM. MODELS APPEAR TO BE IN REASONABLE AGREEMENT WITH THIS
FRONT...WITH LANDFALL SOMETIME AROUND 00Z FRI OR SHORTLY THEREAFTER.
ONE CONCERN WAS THE POTENTIAL FOR HIGH WIND ALONG THE COASTAL
HEADLANDS. PREVIOUS SHIFT HAD ISSUED A HIGH WIND WATCH FOR LATE THIS
AFTERNOON THROUGH 08Z FRI. UPON FURTHER REVIEW...NOT SEEING ENOUGH IN
THE 850 MB TO 950 MB WIND FIELDS TO UPGRADE TO A WARNING. THE 00Z
WRF-GFS VALID 00Z FRI HAS A COASTAL JET SIGNATURE OVER THE OREGON
COASTAL WATERS...WITH FORECAST 10M WIND GUSTS OF 55 KT. HOWEVER...BY
03Z FRI THE MODEL HAS JUST A SMALL SLIVER OF 55 KT GUSTS JUST OFF THE
CENTRAL COAST. WOULD NOT BE SURPRISED TO SEE ISOLATED 55 TO 60 MPH
GUSTS ON EXPOSED HEADLAND AREAS LATE THIS AFTERNOON THROUGH THE
MID-EVENING HOURS...BUT DO NOT THINK THESE WILL BE WIDESPREAD AND
FREQUENT ENOUGH TO WARRANT A WARNING.

THE SYSTEM WILL BRING A 6-9 HR SHOT OF RAIN TO THE AREA...BUT SNOW
LEVELS ARE EXPECTED TO SLOWLY RISE AHEAD OF THE FRONT. THE COLDER
UPPER TROUGH SLIDES ACROSS THE REGION FRI...WITH 1000-500 MB
THICKNESS VALUES DROPPING INTO THE LOW TO MID 530S BY 18Z FRI. THIS
PUTS SNOW LEVELS WELL BELOW THE CASCADE PASSES...BUT BY THIS TIME THE
BULK OF THE PRECIPITATION HAS ALREADY OCCURRED. ALTHOUGH NOT IN THE
FORECAST GRIDS AS OF YET...NEED TO CONSIDER THE POSSIBILITY OF
THUNDERSTORMS FOR FRI. GFS SOUNDING FOR KAST VALID 22Z FRI SHOWS LI
VALUES NEAR 0 BUT A SWEAT INDEX OF 272. THE 1000-750 MB LAPSE RATES
ARE AROUND 7.5C/KM.

MODELS STILL ADVERTISING A CHANGE TO A MUCH WETTER PATTERN STARTING
SAT. NAM AND GFS CONTINUE TO SHOW AN ATMOSPHERIC RIVER SET UP
DIRECTED AT SW WASHINGTON AND NW OREGON SAT. THE GEM MAY BE A BIT
SLOWER...BUT STILL HAS SUBSTANTIAL QPF DIRECTED AT THE FORECAST AREA
BY SAT NIGHT. THE 00Z WRFGFS SHOWS VERY HEAVY QPF WITH UP TO 8-12
INCHES OF RAIN IN THE HIGHER TERRAIN AND 2-4 INCHES IN THE WILLAMETTE
VALLEY SAT THROUGH MONDAY. WILL NEED TO MONITOR THIS VERY CLOSELY
OVER THE NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING
ON AREA MAINSTEM RIVERS.  WEISHAAR

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN THE
MILD AND MOIST ATMOSPHERIC RIVER PATTERN THROUGH AT LEAST SUN. THE
ECMWF AND GEM GRADUALLY SHIFT THE FOCUS OF THE HEAVIEST PRECIP TO THE
N SUN AFTERNOON BUT THE GFS DOES NOT. EXPECT PLENTY OF RAINFALL TO
CONTINUE THROUGH SUNDAY. ON MONDAY AND TUESDAY...SOME WEAK RIDGING
MOVES OVER THE REGION BUT SHOWERS LIKELY CONTINUE IN THE MOIST
ONSHORE FLOW. THE ECMWF THEN INDICATES ANOTHER MAJOR PATTERN CHANGE
AROUND THE MIDDLE OF NEXT WEEK WITH A MUCH COLDER AIR MASS SETTLING
OVER THE PAC NW. HOWEVER...MOISTURE DIMINISHES DUE TO THE DRIER N-NE
FLOW. THUS...AFTER WHATEVER SNOW THE CASCADES GET LATE THIS WEEK...IT
WILL BE LOST OVER THE WEEKEND. THE GFS ALSO HAS A CHANGE TO COLDER
NW-N FLOW ALOFT BUT IT MAINTAINS AN OPEN TROUGH INSTEAD OF THE CLOSED
UPPER LOW ECMWF SOLUTION. WHILE STILL SOME SIGNIFICANT UNCERTAINTY
EXISTS WITH RESPECT TO THE TIMING OF THE COLD AIR AND JUST HOW COLD
THE AIR WILL BE...IT DOES APPEAR THAT A CHANGE TO MUCH COOLER
CONDITIONS WILL MOVE INTO THE REGION. SNOW LEVELS SHOULD BE QUITE LOW
OVER THE HOLIDAY...BUT DROPPED POPS SUBSTANTIALLY NEXT THU AND THU
NIGHT. WEISHAAR

&&

.AVIATION...LIGHT WINDS AND A MOIST LOWER ATMOSPHERE WILL CONTINUE
TO BRING A MIX OF IFR TO VFR CONDITIONS THROUGH LATE THURSDAY
MORNING. AS THE NEXT FRONT APPROACHES AND THE WINDS PICK UP AHEAD
OF IT EXPECT MOST TAF SITES TO IMPROVE TO VFR BY THURSDAY
AFTERNOON. THE FRONT WILL LIKELY PUSH INTO THE COAST AROUND 03Z
FRIDAY...AND INTO THE INTERIOR AROUND 06Z FRIDAY. EXPECT BRIEF
PERIODS OF IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS ASSOCIATED WITH THE FRONT.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PERSIST THROUGH
FRIDAY MORNING. HOWEVER...BRIEF PERIODS OF MVFR CIGS ARE POSSIBLE
THROUGH LATE THURSDAY MORNING DUE TO A MOIST LOWER ATMOSPHERE. A
FRONT WILL PUSH THROUGH AFTER 06Z FRIDAY AND COULD BRING BRIEF
PERIODS TO IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS. /64

&&

.MARINE...SEAS CONTINUED TO HOVER AROUND 10 FT OVERNIGHT AND LOOKS
TO REMAIN ELEVATED THROUGHOUT THE MORNING SO THE SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED TO 1 PM. A STRONG
FRONTAL SYSTEM IS STILL ON TRACK TO MOVE ACROSS THE WATERS TODAY
AND WILL BRING SOLID GALE GUSTS THROUGH THURSDAY NIGHT WITH SEAS
CLIMBING INTO THE MID TEENS. /64

PREVIOUS DISCUSSION FOLLOWS...EXPECT SEAS TO SUBSIDE FAIRLY
QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE THURSDAY NIGHT
INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER WAVE HEIGHTS WILL
BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD WESTERLY SWELL WILL
LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY EVENING. WAVE HEIGHTS
MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS COULD CERTAINLY CATCH
OFF GUARD ANY UNINFORMED MARINERS THAT VENTURE OUT FRIDAY MORNING.
CONFIDENCE IS RELATIVELY HIGH THAT THIS SWELL WILL LIKELY EXCEED
20 FT. IN FACT...THESE PATTERNS OFTEN PRODUCE HIGHER SEAS THAN
FORECASTED BY THE ENP WAVE MODEL. A HIGH SURF ADVISORY APPEARS
LIKELY. THE GOOD NEWS IS THAT THE LARGEST SWELL WILL LIKELY ARRIVE
DURING LOW TIDE AND DURING THE NIGHT TIME HOURS WHEN MOST MARINERS
AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST FRIDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 181216
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
414 AM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL REDEVELOP BY LATE THIS AFTERNOON AND INCREASE
THURSDAY NIGHT AS A MORE ORGANIZED FRONTAL SYSTEM MOVES ONSHORE. A
COLDER UPPER TROUGH MOVES ACROSS THE AREA FRIDAY...WHICH WILL LOWER
SNOW LEVLES BELOW THE CASCADE PASSES. MILD AND VERY WET WEATHER IS
EXPECTED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC RIVER
AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA. THE EXACT
LOCATION OF THE JET STREAM AND ASSOCIATED MOISTURE PLUME ARE STILL IN
DOUBT. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...WATER VAPOR IMAGERY AS OF
1030Z SHOWS A DEEP UPPER LOW IN THE GULF OF ALASKA WITH A FRONTAL
SYSTEM TAKING SHAPE NEAR 135W. THE 06Z NAM12 RUN SHOWS A WEAK SURFACE
LOW OFF THE S OREGON COAST AT 09Z. THIS FEATURE IS VERY DIFFICULT TO
PICK OUT IN THE WATER VAPOR LOOPER. THE NAM SHOWS THIS LOW FILLING
OVERNIGHT AS IT DRIFTS TO THE NE. NWS PORTLAND DUAL-POL DOPPLER RADAR
SHOWING DECREASING RADAR RETURNS...WITH THE STRONGEST ECHOES IN THE
WILLAPA HILLS AND S WA CASCADES.

NAM...GFS AND ECMWF ALL INDICATE A WEAK 500 MB RIDGE TO MOVE ACROSS
THE AREA TODAY. HOWEVER...MODEL CROSS-SECTIONS AND TIME-HEIGHT
FORECASTS MAINTAIN MOIST LOW-LEVELS THROUGH THE DAY. THUS...STILL
EXPECT LIGHT QPF ACROSS THE FORECAST AREA TODAY...AHEAD OF THE NEXT
FRONTAL SYSTEM. MODELS APPEAR TO BE IN REASONABLE AGREEMENT WITH THIS
FRONT...WITH LANDFALL SOMETIME AROUND 00Z FRI OR SHORTLY THEREAFTER.
ONE CONCERN WAS THE POTENTIAL FOR HIGH WIND ALONG THE COASTAL
HEADLANDS. PREVIOUS SHIFT HAD ISSUED A HIGH WIND WATCH FOR LATE THIS
AFTERNOON THROUGH 08Z FRI. UPON FURTHER REVIEW...NOT SEEING ENOUGH IN
THE 850 MB TO 950 MB WIND FIELDS TO UPGRADE TO A WARNING. THE 00Z
WRF-GFS VALID 00Z FRI HAS A COASTAL JET SIGNATURE OVER THE OREGON
COASTAL WATERS...WITH FORECAST 10M WIND GUSTS OF 55 KT. HOWEVER...BY
03Z FRI THE MODEL HAS JUST A SMALL SLIVER OF 55 KT GUSTS JUST OFF THE
CENTRAL COAST. WOULD NOT BE SURPRISED TO SEE ISOLATED 55 TO 60 MPH
GUSTS ON EXPOSED HEADLAND AREAS LATE THIS AFTERNOON THROUGH THE
MID-EVENING HOURS...BUT DO NOT THINK THESE WILL BE WIDESPREAD AND
FREQUENT ENOUGH TO WARRANT A WARNING.

THE SYSTEM WILL BRING A 6-9 HR SHOT OF RAIN TO THE AREA...BUT SNOW
LEVELS ARE EXPECTED TO SLOWLY RISE AHEAD OF THE FRONT. THE COLDER
UPPER TROUGH SLIDES ACROSS THE REGION FRI...WITH 1000-500 MB
THICKNESS VALUES DROPPING INTO THE LOW TO MID 530S BY 18Z FRI. THIS
PUTS SNOW LEVELS WELL BELOW THE CASCADE PASSES...BUT BY THIS TIME THE
BULK OF THE PRECIPITATION HAS ALREADY OCCURRED. ALTHOUGH NOT IN THE
FORECAST GRIDS AS OF YET...NEED TO CONSIDER THE POSSIBILITY OF
THUNDERSTORMS FOR FRI. GFS SOUNDING FOR KAST VALID 22Z FRI SHOWS LI
VALUES NEAR 0 BUT A SWEAT INDEX OF 272. THE 1000-750 MB LAPSE RATES
ARE AROUND 7.5C/KM.

MODELS STILL ADVERTISING A CHANGE TO A MUCH WETTER PATTERN STARTING
SAT. NAM AND GFS CONTINUE TO SHOW AN ATMOSPHERIC RIVER SET UP
DIRECTED AT SW WASHINGTON AND NW OREGON SAT. THE GEM MAY BE A BIT
SLOWER...BUT STILL HAS SUBSTANTIAL QPF DIRECTED AT THE FORECAST AREA
BY SAT NIGHT. THE 00Z WRFGFS SHOWS VERY HEAVY QPF WITH UP TO 8-12
INCHES OF RAIN IN THE HIGHER TERRAIN AND 2-4 INCHES IN THE WILLAMETTE
VALLEY SAT THROUGH MONDAY. WILL NEED TO MONITOR THIS VERY CLOSELY
OVER THE NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING
ON AREA MAINSTEM RIVERS.  WEISHAAR

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN THE
MILD AND MOIST ATMOSPHERIC RIVER PATTERN THROUGH AT LEAST SUN. THE
ECMWF AND GEM GRADUALLY SHIFT THE FOCUS OF THE HEAVIEST PRECIP TO THE
N SUN AFTERNOON BUT THE GFS DOES NOT. EXPECT PLENTY OF RAINFALL TO
CONTINUE THROUGH SUNDAY. ON MONDAY AND TUESDAY...SOME WEAK RIDGING
MOVES OVER THE REGION BUT SHOWERS LIKELY CONTINUE IN THE MOIST
ONSHORE FLOW. THE ECMWF THEN INDICATES ANOTHER MAJOR PATTERN CHANGE
AROUND THE MIDDLE OF NEXT WEEK WITH A MUCH COLDER AIR MASS SETTLING
OVER THE PAC NW. HOWEVER...MOISTURE DIMINISHES DUE TO THE DRIER N-NE
FLOW. THUS...AFTER WHATEVER SNOW THE CASCADES GET LATE THIS WEEK...IT
WILL BE LOST OVER THE WEEKEND. THE GFS ALSO HAS A CHANGE TO COLDER
NW-N FLOW ALOFT BUT IT MAINTAINS AN OPEN TROUGH INSTEAD OF THE CLOSED
UPPER LOW ECMWF SOLUTION. WHILE STILL SOME SIGNIFICANT UNCERTAINTY
EXISTS WITH RESPECT TO THE TIMING OF THE COLD AIR AND JUST HOW COLD
THE AIR WILL BE...IT DOES APPEAR THAT A CHANGE TO MUCH COOLER
CONDITIONS WILL MOVE INTO THE REGION. SNOW LEVELS SHOULD BE QUITE LOW
OVER THE HOLIDAY...BUT DROPPED POPS SUBSTANTIALLY NEXT THU AND THU
NIGHT. WEISHAAR

&&

.AVIATION...LIGHT WINDS AND A MOIST LOWER ATMOSPHERE WILL CONTINUE
TO BRING A MIX OF IFR TO VFR CONDITIONS THROUGH LATE THURSDAY
MORNING. AS THE NEXT FRONT APPROACHES AND THE WINDS PICK UP AHEAD
OF IT EXPECT MOST TAF SITES TO IMPROVE TO VFR BY THURSDAY
AFTERNOON. THE FRONT WILL LIKELY PUSH INTO THE COAST AROUND 03Z
FRIDAY...AND INTO THE INTERIOR AROUND 06Z FRIDAY. EXPECT BRIEF
PERIODS OF IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS ASSOCIATED WITH THE FRONT.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PERSIST THROUGH
FRIDAY MORNING. HOWEVER...BRIEF PERIODS OF MVFR CIGS ARE POSSIBLE
THROUGH LATE THURSDAY MORNING DUE TO A MOIST LOWER ATMOSPHERE. A
FRONT WILL PUSH THROUGH AFTER 06Z FRIDAY AND COULD BRING BRIEF
PERIODS TO IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS. /64

&&

.MARINE...SEAS CONTINUED TO HOVER AROUND 10 FT OVERNIGHT AND LOOKS
TO REMAIN ELEVATED THROUGHOUT THE MORNING SO THE SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED TO 1 PM. A STRONG
FRONTAL SYSTEM IS STILL ON TRACK TO MOVE ACROSS THE WATERS TODAY
AND WILL BRING SOLID GALE GUSTS THROUGH THURSDAY NIGHT WITH SEAS
CLIMBING INTO THE MID TEENS. /64

PREVIOUS DISCUSSION FOLLOWS...EXPECT SEAS TO SUBSIDE FAIRLY
QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE THURSDAY NIGHT
INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER WAVE HEIGHTS WILL
BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD WESTERLY SWELL WILL
LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY EVENING. WAVE HEIGHTS
MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS COULD CERTAINLY CATCH
OFF GUARD ANY UNINFORMED MARINERS THAT VENTURE OUT FRIDAY MORNING.
CONFIDENCE IS RELATIVELY HIGH THAT THIS SWELL WILL LIKELY EXCEED
20 FT. IN FACT...THESE PATTERNS OFTEN PRODUCE HIGHER SEAS THAN
FORECASTED BY THE ENP WAVE MODEL. A HIGH SURF ADVISORY APPEARS
LIKELY. THE GOOD NEWS IS THAT THE LARGEST SWELL WILL LIKELY ARRIVE
DURING LOW TIDE AND DURING THE NIGHT TIME HOURS WHEN MOST MARINERS
AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST FRIDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 181216
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
414 AM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL REDEVELOP BY LATE THIS AFTERNOON AND INCREASE
THURSDAY NIGHT AS A MORE ORGANIZED FRONTAL SYSTEM MOVES ONSHORE. A
COLDER UPPER TROUGH MOVES ACROSS THE AREA FRIDAY...WHICH WILL LOWER
SNOW LEVLES BELOW THE CASCADE PASSES. MILD AND VERY WET WEATHER IS
EXPECTED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC RIVER
AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA. THE EXACT
LOCATION OF THE JET STREAM AND ASSOCIATED MOISTURE PLUME ARE STILL IN
DOUBT. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...WATER VAPOR IMAGERY AS OF
1030Z SHOWS A DEEP UPPER LOW IN THE GULF OF ALASKA WITH A FRONTAL
SYSTEM TAKING SHAPE NEAR 135W. THE 06Z NAM12 RUN SHOWS A WEAK SURFACE
LOW OFF THE S OREGON COAST AT 09Z. THIS FEATURE IS VERY DIFFICULT TO
PICK OUT IN THE WATER VAPOR LOOPER. THE NAM SHOWS THIS LOW FILLING
OVERNIGHT AS IT DRIFTS TO THE NE. NWS PORTLAND DUAL-POL DOPPLER RADAR
SHOWING DECREASING RADAR RETURNS...WITH THE STRONGEST ECHOES IN THE
WILLAPA HILLS AND S WA CASCADES.

NAM...GFS AND ECMWF ALL INDICATE A WEAK 500 MB RIDGE TO MOVE ACROSS
THE AREA TODAY. HOWEVER...MODEL CROSS-SECTIONS AND TIME-HEIGHT
FORECASTS MAINTAIN MOIST LOW-LEVELS THROUGH THE DAY. THUS...STILL
EXPECT LIGHT QPF ACROSS THE FORECAST AREA TODAY...AHEAD OF THE NEXT
FRONTAL SYSTEM. MODELS APPEAR TO BE IN REASONABLE AGREEMENT WITH THIS
FRONT...WITH LANDFALL SOMETIME AROUND 00Z FRI OR SHORTLY THEREAFTER.
ONE CONCERN WAS THE POTENTIAL FOR HIGH WIND ALONG THE COASTAL
HEADLANDS. PREVIOUS SHIFT HAD ISSUED A HIGH WIND WATCH FOR LATE THIS
AFTERNOON THROUGH 08Z FRI. UPON FURTHER REVIEW...NOT SEEING ENOUGH IN
THE 850 MB TO 950 MB WIND FIELDS TO UPGRADE TO A WARNING. THE 00Z
WRF-GFS VALID 00Z FRI HAS A COASTAL JET SIGNATURE OVER THE OREGON
COASTAL WATERS...WITH FORECAST 10M WIND GUSTS OF 55 KT. HOWEVER...BY
03Z FRI THE MODEL HAS JUST A SMALL SLIVER OF 55 KT GUSTS JUST OFF THE
CENTRAL COAST. WOULD NOT BE SURPRISED TO SEE ISOLATED 55 TO 60 MPH
GUSTS ON EXPOSED HEADLAND AREAS LATE THIS AFTERNOON THROUGH THE
MID-EVENING HOURS...BUT DO NOT THINK THESE WILL BE WIDESPREAD AND
FREQUENT ENOUGH TO WARRANT A WARNING.

THE SYSTEM WILL BRING A 6-9 HR SHOT OF RAIN TO THE AREA...BUT SNOW
LEVELS ARE EXPECTED TO SLOWLY RISE AHEAD OF THE FRONT. THE COLDER
UPPER TROUGH SLIDES ACROSS THE REGION FRI...WITH 1000-500 MB
THICKNESS VALUES DROPPING INTO THE LOW TO MID 530S BY 18Z FRI. THIS
PUTS SNOW LEVELS WELL BELOW THE CASCADE PASSES...BUT BY THIS TIME THE
BULK OF THE PRECIPITATION HAS ALREADY OCCURRED. ALTHOUGH NOT IN THE
FORECAST GRIDS AS OF YET...NEED TO CONSIDER THE POSSIBILITY OF
THUNDERSTORMS FOR FRI. GFS SOUNDING FOR KAST VALID 22Z FRI SHOWS LI
VALUES NEAR 0 BUT A SWEAT INDEX OF 272. THE 1000-750 MB LAPSE RATES
ARE AROUND 7.5C/KM.

MODELS STILL ADVERTISING A CHANGE TO A MUCH WETTER PATTERN STARTING
SAT. NAM AND GFS CONTINUE TO SHOW AN ATMOSPHERIC RIVER SET UP
DIRECTED AT SW WASHINGTON AND NW OREGON SAT. THE GEM MAY BE A BIT
SLOWER...BUT STILL HAS SUBSTANTIAL QPF DIRECTED AT THE FORECAST AREA
BY SAT NIGHT. THE 00Z WRFGFS SHOWS VERY HEAVY QPF WITH UP TO 8-12
INCHES OF RAIN IN THE HIGHER TERRAIN AND 2-4 INCHES IN THE WILLAMETTE
VALLEY SAT THROUGH MONDAY. WILL NEED TO MONITOR THIS VERY CLOSELY
OVER THE NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING
ON AREA MAINSTEM RIVERS.  WEISHAAR

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN THE
MILD AND MOIST ATMOSPHERIC RIVER PATTERN THROUGH AT LEAST SUN. THE
ECMWF AND GEM GRADUALLY SHIFT THE FOCUS OF THE HEAVIEST PRECIP TO THE
N SUN AFTERNOON BUT THE GFS DOES NOT. EXPECT PLENTY OF RAINFALL TO
CONTINUE THROUGH SUNDAY. ON MONDAY AND TUESDAY...SOME WEAK RIDGING
MOVES OVER THE REGION BUT SHOWERS LIKELY CONTINUE IN THE MOIST
ONSHORE FLOW. THE ECMWF THEN INDICATES ANOTHER MAJOR PATTERN CHANGE
AROUND THE MIDDLE OF NEXT WEEK WITH A MUCH COLDER AIR MASS SETTLING
OVER THE PAC NW. HOWEVER...MOISTURE DIMINISHES DUE TO THE DRIER N-NE
FLOW. THUS...AFTER WHATEVER SNOW THE CASCADES GET LATE THIS WEEK...IT
WILL BE LOST OVER THE WEEKEND. THE GFS ALSO HAS A CHANGE TO COLDER
NW-N FLOW ALOFT BUT IT MAINTAINS AN OPEN TROUGH INSTEAD OF THE CLOSED
UPPER LOW ECMWF SOLUTION. WHILE STILL SOME SIGNIFICANT UNCERTAINTY
EXISTS WITH RESPECT TO THE TIMING OF THE COLD AIR AND JUST HOW COLD
THE AIR WILL BE...IT DOES APPEAR THAT A CHANGE TO MUCH COOLER
CONDITIONS WILL MOVE INTO THE REGION. SNOW LEVELS SHOULD BE QUITE LOW
OVER THE HOLIDAY...BUT DROPPED POPS SUBSTANTIALLY NEXT THU AND THU
NIGHT. WEISHAAR

&&

.AVIATION...LIGHT WINDS AND A MOIST LOWER ATMOSPHERE WILL CONTINUE
TO BRING A MIX OF IFR TO VFR CONDITIONS THROUGH LATE THURSDAY
MORNING. AS THE NEXT FRONT APPROACHES AND THE WINDS PICK UP AHEAD
OF IT EXPECT MOST TAF SITES TO IMPROVE TO VFR BY THURSDAY
AFTERNOON. THE FRONT WILL LIKELY PUSH INTO THE COAST AROUND 03Z
FRIDAY...AND INTO THE INTERIOR AROUND 06Z FRIDAY. EXPECT BRIEF
PERIODS OF IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS ASSOCIATED WITH THE FRONT.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PERSIST THROUGH
FRIDAY MORNING. HOWEVER...BRIEF PERIODS OF MVFR CIGS ARE POSSIBLE
THROUGH LATE THURSDAY MORNING DUE TO A MOIST LOWER ATMOSPHERE. A
FRONT WILL PUSH THROUGH AFTER 06Z FRIDAY AND COULD BRING BRIEF
PERIODS TO IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS. /64

&&

.MARINE...SEAS CONTINUED TO HOVER AROUND 10 FT OVERNIGHT AND LOOKS
TO REMAIN ELEVATED THROUGHOUT THE MORNING SO THE SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED TO 1 PM. A STRONG
FRONTAL SYSTEM IS STILL ON TRACK TO MOVE ACROSS THE WATERS TODAY
AND WILL BRING SOLID GALE GUSTS THROUGH THURSDAY NIGHT WITH SEAS
CLIMBING INTO THE MID TEENS. /64

PREVIOUS DISCUSSION FOLLOWS...EXPECT SEAS TO SUBSIDE FAIRLY
QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE THURSDAY NIGHT
INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER WAVE HEIGHTS WILL
BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD WESTERLY SWELL WILL
LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY EVENING. WAVE HEIGHTS
MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS COULD CERTAINLY CATCH
OFF GUARD ANY UNINFORMED MARINERS THAT VENTURE OUT FRIDAY MORNING.
CONFIDENCE IS RELATIVELY HIGH THAT THIS SWELL WILL LIKELY EXCEED
20 FT. IN FACT...THESE PATTERNS OFTEN PRODUCE HIGHER SEAS THAN
FORECASTED BY THE ENP WAVE MODEL. A HIGH SURF ADVISORY APPEARS
LIKELY. THE GOOD NEWS IS THAT THE LARGEST SWELL WILL LIKELY ARRIVE
DURING LOW TIDE AND DURING THE NIGHT TIME HOURS WHEN MOST MARINERS
AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST FRIDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 181216
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
414 AM PST THU DEC 18 2014

.SYNOPSIS...RAIN WILL REDEVELOP BY LATE THIS AFTERNOON AND INCREASE
THURSDAY NIGHT AS A MORE ORGANIZED FRONTAL SYSTEM MOVES ONSHORE. A
COLDER UPPER TROUGH MOVES ACROSS THE AREA FRIDAY...WHICH WILL LOWER
SNOW LEVLES BELOW THE CASCADE PASSES. MILD AND VERY WET WEATHER IS
EXPECTED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC RIVER
AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA. THE EXACT
LOCATION OF THE JET STREAM AND ASSOCIATED MOISTURE PLUME ARE STILL IN
DOUBT. THERE IS THE POTENTIAL FOR SOME FLOODING LATE THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...WATER VAPOR IMAGERY AS OF
1030Z SHOWS A DEEP UPPER LOW IN THE GULF OF ALASKA WITH A FRONTAL
SYSTEM TAKING SHAPE NEAR 135W. THE 06Z NAM12 RUN SHOWS A WEAK SURFACE
LOW OFF THE S OREGON COAST AT 09Z. THIS FEATURE IS VERY DIFFICULT TO
PICK OUT IN THE WATER VAPOR LOOPER. THE NAM SHOWS THIS LOW FILLING
OVERNIGHT AS IT DRIFTS TO THE NE. NWS PORTLAND DUAL-POL DOPPLER RADAR
SHOWING DECREASING RADAR RETURNS...WITH THE STRONGEST ECHOES IN THE
WILLAPA HILLS AND S WA CASCADES.

NAM...GFS AND ECMWF ALL INDICATE A WEAK 500 MB RIDGE TO MOVE ACROSS
THE AREA TODAY. HOWEVER...MODEL CROSS-SECTIONS AND TIME-HEIGHT
FORECASTS MAINTAIN MOIST LOW-LEVELS THROUGH THE DAY. THUS...STILL
EXPECT LIGHT QPF ACROSS THE FORECAST AREA TODAY...AHEAD OF THE NEXT
FRONTAL SYSTEM. MODELS APPEAR TO BE IN REASONABLE AGREEMENT WITH THIS
FRONT...WITH LANDFALL SOMETIME AROUND 00Z FRI OR SHORTLY THEREAFTER.
ONE CONCERN WAS THE POTENTIAL FOR HIGH WIND ALONG THE COASTAL
HEADLANDS. PREVIOUS SHIFT HAD ISSUED A HIGH WIND WATCH FOR LATE THIS
AFTERNOON THROUGH 08Z FRI. UPON FURTHER REVIEW...NOT SEEING ENOUGH IN
THE 850 MB TO 950 MB WIND FIELDS TO UPGRADE TO A WARNING. THE 00Z
WRF-GFS VALID 00Z FRI HAS A COASTAL JET SIGNATURE OVER THE OREGON
COASTAL WATERS...WITH FORECAST 10M WIND GUSTS OF 55 KT. HOWEVER...BY
03Z FRI THE MODEL HAS JUST A SMALL SLIVER OF 55 KT GUSTS JUST OFF THE
CENTRAL COAST. WOULD NOT BE SURPRISED TO SEE ISOLATED 55 TO 60 MPH
GUSTS ON EXPOSED HEADLAND AREAS LATE THIS AFTERNOON THROUGH THE
MID-EVENING HOURS...BUT DO NOT THINK THESE WILL BE WIDESPREAD AND
FREQUENT ENOUGH TO WARRANT A WARNING.

THE SYSTEM WILL BRING A 6-9 HR SHOT OF RAIN TO THE AREA...BUT SNOW
LEVELS ARE EXPECTED TO SLOWLY RISE AHEAD OF THE FRONT. THE COLDER
UPPER TROUGH SLIDES ACROSS THE REGION FRI...WITH 1000-500 MB
THICKNESS VALUES DROPPING INTO THE LOW TO MID 530S BY 18Z FRI. THIS
PUTS SNOW LEVELS WELL BELOW THE CASCADE PASSES...BUT BY THIS TIME THE
BULK OF THE PRECIPITATION HAS ALREADY OCCURRED. ALTHOUGH NOT IN THE
FORECAST GRIDS AS OF YET...NEED TO CONSIDER THE POSSIBILITY OF
THUNDERSTORMS FOR FRI. GFS SOUNDING FOR KAST VALID 22Z FRI SHOWS LI
VALUES NEAR 0 BUT A SWEAT INDEX OF 272. THE 1000-750 MB LAPSE RATES
ARE AROUND 7.5C/KM.

MODELS STILL ADVERTISING A CHANGE TO A MUCH WETTER PATTERN STARTING
SAT. NAM AND GFS CONTINUE TO SHOW AN ATMOSPHERIC RIVER SET UP
DIRECTED AT SW WASHINGTON AND NW OREGON SAT. THE GEM MAY BE A BIT
SLOWER...BUT STILL HAS SUBSTANTIAL QPF DIRECTED AT THE FORECAST AREA
BY SAT NIGHT. THE 00Z WRFGFS SHOWS VERY HEAVY QPF WITH UP TO 8-12
INCHES OF RAIN IN THE HIGHER TERRAIN AND 2-4 INCHES IN THE WILLAMETTE
VALLEY SAT THROUGH MONDAY. WILL NEED TO MONITOR THIS VERY CLOSELY
OVER THE NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING
ON AREA MAINSTEM RIVERS.  WEISHAAR

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN THE
MILD AND MOIST ATMOSPHERIC RIVER PATTERN THROUGH AT LEAST SUN. THE
ECMWF AND GEM GRADUALLY SHIFT THE FOCUS OF THE HEAVIEST PRECIP TO THE
N SUN AFTERNOON BUT THE GFS DOES NOT. EXPECT PLENTY OF RAINFALL TO
CONTINUE THROUGH SUNDAY. ON MONDAY AND TUESDAY...SOME WEAK RIDGING
MOVES OVER THE REGION BUT SHOWERS LIKELY CONTINUE IN THE MOIST
ONSHORE FLOW. THE ECMWF THEN INDICATES ANOTHER MAJOR PATTERN CHANGE
AROUND THE MIDDLE OF NEXT WEEK WITH A MUCH COLDER AIR MASS SETTLING
OVER THE PAC NW. HOWEVER...MOISTURE DIMINISHES DUE TO THE DRIER N-NE
FLOW. THUS...AFTER WHATEVER SNOW THE CASCADES GET LATE THIS WEEK...IT
WILL BE LOST OVER THE WEEKEND. THE GFS ALSO HAS A CHANGE TO COLDER
NW-N FLOW ALOFT BUT IT MAINTAINS AN OPEN TROUGH INSTEAD OF THE CLOSED
UPPER LOW ECMWF SOLUTION. WHILE STILL SOME SIGNIFICANT UNCERTAINTY
EXISTS WITH RESPECT TO THE TIMING OF THE COLD AIR AND JUST HOW COLD
THE AIR WILL BE...IT DOES APPEAR THAT A CHANGE TO MUCH COOLER
CONDITIONS WILL MOVE INTO THE REGION. SNOW LEVELS SHOULD BE QUITE LOW
OVER THE HOLIDAY...BUT DROPPED POPS SUBSTANTIALLY NEXT THU AND THU
NIGHT. WEISHAAR

&&

.AVIATION...LIGHT WINDS AND A MOIST LOWER ATMOSPHERE WILL CONTINUE
TO BRING A MIX OF IFR TO VFR CONDITIONS THROUGH LATE THURSDAY
MORNING. AS THE NEXT FRONT APPROACHES AND THE WINDS PICK UP AHEAD
OF IT EXPECT MOST TAF SITES TO IMPROVE TO VFR BY THURSDAY
AFTERNOON. THE FRONT WILL LIKELY PUSH INTO THE COAST AROUND 03Z
FRIDAY...AND INTO THE INTERIOR AROUND 06Z FRIDAY. EXPECT BRIEF
PERIODS OF IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS ASSOCIATED WITH THE FRONT.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TO PERSIST THROUGH
FRIDAY MORNING. HOWEVER...BRIEF PERIODS OF MVFR CIGS ARE POSSIBLE
THROUGH LATE THURSDAY MORNING DUE TO A MOIST LOWER ATMOSPHERE. A
FRONT WILL PUSH THROUGH AFTER 06Z FRIDAY AND COULD BRING BRIEF
PERIODS TO IFR TO MVFR CIGS AND VIS UNDER LIGHT TO MODERATE RAIN
BANDS. /64

&&

.MARINE...SEAS CONTINUED TO HOVER AROUND 10 FT OVERNIGHT AND LOOKS
TO REMAIN ELEVATED THROUGHOUT THE MORNING SO THE SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED TO 1 PM. A STRONG
FRONTAL SYSTEM IS STILL ON TRACK TO MOVE ACROSS THE WATERS TODAY
AND WILL BRING SOLID GALE GUSTS THROUGH THURSDAY NIGHT WITH SEAS
CLIMBING INTO THE MID TEENS. /64

PREVIOUS DISCUSSION FOLLOWS...EXPECT SEAS TO SUBSIDE FAIRLY
QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE THURSDAY NIGHT
INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER WAVE HEIGHTS WILL
BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD WESTERLY SWELL WILL
LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY EVENING. WAVE HEIGHTS
MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS COULD CERTAINLY CATCH
OFF GUARD ANY UNINFORMED MARINERS THAT VENTURE OUT FRIDAY MORNING.
CONFIDENCE IS RELATIVELY HIGH THAT THIS SWELL WILL LIKELY EXCEED
20 FT. IN FACT...THESE PATTERNS OFTEN PRODUCE HIGHER SEAS THAN
FORECASTED BY THE ENP WAVE MODEL. A HIGH SURF ADVISORY APPEARS
LIKELY. THE GOOD NEWS IS THAT THE LARGEST SWELL WILL LIKELY ARRIVE
DURING LOW TIDE AND DURING THE NIGHT TIME HOURS WHEN MOST MARINERS
AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THIS AFTERNOON FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST TONIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 1 PM PST THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST FRIDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.



000
FXUS66 KOTX 181151
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
351 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
12Z TAFS: Light rain and snow showers will be possible across the
eastern TAF sites through 15-16z this morning with MVFR/VFR
conditions for KGEG-KCOE corridor and KPUW...VFR conditions at
KLWS. Improvements in both cigs/vsby expected after 18-20z.
Further to the west the southeast gradient will keep cigs/vsby
mainly VFR with conditions slipping to IFR at times through the
morning. These conditions should also improve after 20z. Another
weather system will increase the moisture and chances for
precipitaion beginning at KEAT around 03z and spreading east.
Although the best chance for the eastern TAF sites may hold off
until after 12z. This will result in another deterioration in
cigs/vsby. Precipitation as a rain/snow mix at KEAT but turning
to quickly to -RA...otherwise precip as -RA. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 181151
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
351 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
12Z TAFS: Light rain and snow showers will be possible across the
eastern TAF sites through 15-16z this morning with MVFR/VFR
conditions for KGEG-KCOE corridor and KPUW...VFR conditions at
KLWS. Improvements in both cigs/vsby expected after 18-20z.
Further to the west the southeast gradient will keep cigs/vsby
mainly VFR with conditions slipping to IFR at times through the
morning. These conditions should also improve after 20z. Another
weather system will increase the moisture and chances for
precipitaion beginning at KEAT around 03z and spreading east.
Although the best chance for the eastern TAF sites may hold off
until after 12z. This will result in another deterioration in
cigs/vsby. Precipitation as a rain/snow mix at KEAT but turning
to quickly to -RA...otherwise precip as -RA. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 181151
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
351 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
12Z TAFS: Light rain and snow showers will be possible across the
eastern TAF sites through 15-16z this morning with MVFR/VFR
conditions for KGEG-KCOE corridor and KPUW...VFR conditions at
KLWS. Improvements in both cigs/vsby expected after 18-20z.
Further to the west the southeast gradient will keep cigs/vsby
mainly VFR with conditions slipping to IFR at times through the
morning. These conditions should also improve after 20z. Another
weather system will increase the moisture and chances for
precipitaion beginning at KEAT around 03z and spreading east.
Although the best chance for the eastern TAF sites may hold off
until after 12z. This will result in another deterioration in
cigs/vsby. Precipitation as a rain/snow mix at KEAT but turning
to quickly to -RA...otherwise precip as -RA. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 181151
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
351 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
12Z TAFS: Light rain and snow showers will be possible across the
eastern TAF sites through 15-16z this morning with MVFR/VFR
conditions for KGEG-KCOE corridor and KPUW...VFR conditions at
KLWS. Improvements in both cigs/vsby expected after 18-20z.
Further to the west the southeast gradient will keep cigs/vsby
mainly VFR with conditions slipping to IFR at times through the
morning. These conditions should also improve after 20z. Another
weather system will increase the moisture and chances for
precipitaion beginning at KEAT around 03z and spreading east.
Although the best chance for the eastern TAF sites may hold off
until after 12z. This will result in another deterioration in
cigs/vsby. Precipitation as a rain/snow mix at KEAT but turning
to quickly to -RA...otherwise precip as -RA. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 181151
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
351 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
12Z TAFS: Light rain and snow showers will be possible across the
eastern TAF sites through 15-16z this morning with MVFR/VFR
conditions for KGEG-KCOE corridor and KPUW...VFR conditions at
KLWS. Improvements in both cigs/vsby expected after 18-20z.
Further to the west the southeast gradient will keep cigs/vsby
mainly VFR with conditions slipping to IFR at times through the
morning. These conditions should also improve after 20z. Another
weather system will increase the moisture and chances for
precipitaion beginning at KEAT around 03z and spreading east.
Although the best chance for the eastern TAF sites may hold off
until after 12z. This will result in another deterioration in
cigs/vsby. Precipitation as a rain/snow mix at KEAT but turning
to quickly to -RA...otherwise precip as -RA. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 181151
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
351 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will be stubborn in the northern
valleys, especially in the Cascade valleys where some light to
moderate snow is possible. Warming increases Saturday night into
Sunday, making it a mainly rain/high mountain snow event by Sunday
afternoon. In this transition, there is a small chance of a wintry
mix with pockets of freezing rain in a few of the Cascade valleys.
The 850mb 0C line pushes to the Canadian border on Sunday. Sunday
appears to be the warmest day with widespread 40s and a few 50s
possible. QPF looks juicy with a 0.25" to 0.40" possible from
Saturday afternoon into Sunday morning. Gusty winds will increase
Saturday night into Sunday evening with speeds 25-40 kts across
the Columbia Basin. Gusty winds will continue in the mountains
through night, especially in the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
12Z TAFS: Light rain and snow showers will be possible across the
eastern TAF sites through 15-16z this morning with MVFR/VFR
conditions for KGEG-KCOE corridor and KPUW...VFR conditions at
KLWS. Improvements in both cigs/vsby expected after 18-20z.
Further to the west the southeast gradient will keep cigs/vsby
mainly VFR with conditions slipping to IFR at times through the
morning. These conditions should also improve after 20z. Another
weather system will increase the moisture and chances for
precipitaion beginning at KEAT around 03z and spreading east.
Although the best chance for the eastern TAF sites may hold off
until after 12z. This will result in another deterioration in
cigs/vsby. Precipitation as a rain/snow mix at KEAT but turning
to quickly to -RA...otherwise precip as -RA. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KSEW 181102
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
302 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...A FRONTAL SYSTEM OFFSHORE APPROACHING 130W WILL BRING
A CHANCE OF RAIN TODAY...AND WILL SPREAD MORE CONTINUOUS RAIN OVER
THE AREA LATER THIS AFTERNOON. THE COLD FRONT DOES NOT LOOK ALL THAT
STRONG ON IR IMAGERY SO CHANCE POPS LOOK FINE FOR THIS MORNING AND
PROBABLY MUCH OF THE AFTERNOON. THE WETTEST PERIOD WILL BE TONIGHT
AS THE COLD FRONT CROSSES W WA. SNOW LEVELS ARE JUST LOW ENOUGH SO
THAT THE HIGHER ROADS TO MT BAKER AND MT RAINIER MAY RECEIVE
BORDERLINE SNOW ADVISORY AMOUNTS. STEVENS PASS MAY GET A FEW INCHES
OF SNOW LATE TONIGHT BUT SNOQUALMIE WILL PROBABLY JUST SEE RAIN.

THE TRAILING UPPER LEVEL TROUGH NEAR 140W-145W AT 09Z WILL CROSS W
WA ON FRIDAY. IR IMAGERY SHOWS THE AIR MASS IN THE TROUGH TO BE
NICELY UNSTABLE...WHICH WILL BE GOOD FOR SHOWER DEVELOPMENT AS IT
MOVES INLAND. LIKELY POPS FOR FRIDAY MORNING DECREASING TO CHANCE
POPS IN THE AFTERNOON AS THE TROUGH MOVES EAST LOOK FINE. LIFTED
INDICES ARE MARGINAL FOR THUNDERSTORMS OVER THE COASTAL WATERS. THE
LAND AREAS ARE COOL ENOUGH SO THAT THUNDER IS UNLIKELY.

VERY STRONG ZONAL FLOW DEVELOPS ACROSS THE NE PACIFIC FRIDAY NIGHT
AND CONTINUES THROUGH THE WEEKEND. 300 MB ISOTACHS ARE IN THE
160-170KT RANGE. A STRONG WET WARM FRONT ASSOCIATED WITH THE 130KT
NOSE OF THE JET STREAK WILL MOVE ACROSS W WA ON SATURDAY. MODELS ARE
IN FAIR AGREEMENT WITH THE STRENGTH AND GENERAL TIMING OF THIS
FEATURE. THIS WARM FRONT SHOULD GENERATE WIND ADVISORY LEVEL WINDS
OVER THE COAST AND N INTERIOR AND HEAVY RAIN OVER THE COAST AND
MOUNTAINS.

ALTHOUGH THERE WILL BE 2-3 INCHES OF HEAVY RAIN DURING THE 24 HOUR
PERIOD FROM 12Z SATURDAY-12Z SUNDAY...SO FAR IT LOOKS LIKE PRIMARILY
THE SKOKOMISH RIVER MAY BE AT RISK FOR FLOODING.

SNOW LEVELS START OUT NEAR 3000 FEET ON SATURDAY...AND WILL RISE TO
5500 TO 7000 FEET BY SATURDAY NIGHT. THERE COULD BE ENOUGH SNOW IN
THE TRANSITION TO PRODUCE BORDERLINE SNOW ADVISORY AMOUNTS OVER MT
BAKER AND MT RAINIER AGAIN. KAM

.LONG TERM...ECMWF AND GFS SHOW STRONG ZONAL FLOW CONTINUING INTO
EARLY NEXT WEEK WITH A BROAD FLAT UPPER LEVEL RIDGE OVER THE REGION.
LOTS OF FLOW THROUGH THE RIDGE WILL KEEP THIS A GENERALLY WET AND
BREEZY PERIOD THROUGH SUNDAY. THE MAIN PROBLEM WILL REMAIN HEAVY
RAIN SATURDAY NIGHT. FAIRLY STRONG WESTERLY 850 MB FLOW WILL REMAIN
30-45KT SATURDAY NIGHT INTO SUNDAY MORNING...THEN GRADUALLY DIMINISH
OVER THE NORTH AND CENTRAL PART OF W WA SUNDAY AFTERNOON. STRONGER W
FLOW WILL CONTINUE OVER NW OREGON AND THE SOUTHERN WA CASCADES.
THERE COULD BE ANOTHER 2-3 INCHES OF QPF OVER THE CENTRAL CASCADES
12Z SUNDAY THROUGH 12Z MONDAY WHICH COULD BRING SOME CASCADE RIVERS
CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH FRIDAY NIGHT. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. A
STRONG WARM FRONT WILL CROSS THE AREA SATURDAY WITH STRONG S FLOW
OVER THE OLYMPICS BECOMING W BY LATE AFTERNOON. THE STRONG W FLOW
WILL REACH THE CASCADES SATURDAY NIGHT. 2-3 INCHES OF RAIN ARE
EXPECTED OVER THE OLYMPICS AND PARTS OF THE CASCADES DURING THE 24
HOUR PERIOD FROM 12Z SATURDAY THROUGH 12Z SUNDAY. THIS COULD CAUSE
ANOTHER ROUND OF FLOODING ON THE SKOKOMISH RIVER AND PRIME SOME OF
THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH IS MOVING EAST OF THE CASCADES
EARLY THIS MORNING WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS IS
MOIST AND STABLE WITH WEAK SURFACE GRADIENTS. A COLD FRONT ABOUT 500
NM WEST OF SEATTLE AT 09Z WILL PUSH INTO THE REGION THIS EVENING
WITH STRONG SOUTHWEST FLOW ALOFT.

AREAS OF LIGHT RAIN REMAIN ACROSS THE REGION THIS MORNING WITH
WIDESPREAD LOW MVFR AND AREAS OF IFR. SOME TEMPORARY IMPROVEMENT TO
VFR IS POSSIBLE MIDDAY TODAY AS A TRANSITORY UPPER RIDGE MOVES OVER
THE AREA AND SURFACE GRADIENTS BECOME INCREASINGLY OFFSHORE.
WIDESPREAD RAIN WILL RAPIDLY SPREAD BACK INTO THE AREA BY EARLY
EVENING AHEAD OF THE NEXT FRONT WITH CEILINGS FALLING BACK TO MVFR.

KSEA...LOW MVFR AND TEMPO IFR CEILINGS EXPECTED THIS MORNING WITH
LIGHT RAIN SHOWERS AND SURFACE VSBYS OF 3-5SM AT TIMES. VFR CEILINGS
AT OR ABOVE 5K FEET POSSIBLE 18Z-00Z BUT WILL DROP AGAIN WITH MORE
RAIN THIS EVENING. LIGHT SOUTH-SOUTHEAST WIND THIS
MORNING...BECOMING SOUTHEAST 7 TO 12 KNOTS IN THE AFTERNOON AND
EVENING. 27

&&

.MARINE...A FRONT ASSOCIATED WITH A 970-975 MB LOW WELL WEST OF
HAIDA GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN
INLAND TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER
THE COASTAL WATERS MIDDAY TODAY THROUGH THIS EVENING WITH SMALL
CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. SOME MESOSCALE MODELS INDICATE A BRIEF
PERIOD OF GALE FORCE WIND POSSIBLE AT THE EAST ENTRANCE TO THE
STRAIT AND THE VICINITY OF THE SAN JUANS THIS EVENING JUST AHEAD OF
THE FRONT. INCREASING SOUTHERLY GRADIENT BEHIND THE FRONT WILL BRING
SMALL CRAFT ADVISORY WINDS TO PUGET SOUND AND HOOD CANAL TONIGHT. A
LONG PERIOD SWELL NEAR 22 FEET IS STILL EXPECTED ON THE COAST LATE
FRIDAY AFTERNOON OR FRIDAY NIGHT. TIDAL ANOMALIES ALONG THE COAST
ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH TIDE OCCURS SATURDAY
MORNING. IF SWELL REMAINS HIGH INTO SATURDAY MORNING AS CURRENTLY
EXPECTED...SOME COASTAL FLOODING IS POSSIBLE. ANOTHER STRONG FRONT
WILL ARRIVE ON SATURDAY WITH GALE FORCE WINDS ONCE AGAIN LIKELY OVER
THE COASTAL WATERS...THE NORTHERN INLAND WATERS...AND THE STRAIT
ENTRANCES. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








000
FXUS66 KSEW 181102
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
302 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...A FRONTAL SYSTEM OFFSHORE APPROACHING 130W WILL BRING
A CHANCE OF RAIN TODAY...AND WILL SPREAD MORE CONTINUOUS RAIN OVER
THE AREA LATER THIS AFTERNOON. THE COLD FRONT DOES NOT LOOK ALL THAT
STRONG ON IR IMAGERY SO CHANCE POPS LOOK FINE FOR THIS MORNING AND
PROBABLY MUCH OF THE AFTERNOON. THE WETTEST PERIOD WILL BE TONIGHT
AS THE COLD FRONT CROSSES W WA. SNOW LEVELS ARE JUST LOW ENOUGH SO
THAT THE HIGHER ROADS TO MT BAKER AND MT RAINIER MAY RECEIVE
BORDERLINE SNOW ADVISORY AMOUNTS. STEVENS PASS MAY GET A FEW INCHES
OF SNOW LATE TONIGHT BUT SNOQUALMIE WILL PROBABLY JUST SEE RAIN.

THE TRAILING UPPER LEVEL TROUGH NEAR 140W-145W AT 09Z WILL CROSS W
WA ON FRIDAY. IR IMAGERY SHOWS THE AIR MASS IN THE TROUGH TO BE
NICELY UNSTABLE...WHICH WILL BE GOOD FOR SHOWER DEVELOPMENT AS IT
MOVES INLAND. LIKELY POPS FOR FRIDAY MORNING DECREASING TO CHANCE
POPS IN THE AFTERNOON AS THE TROUGH MOVES EAST LOOK FINE. LIFTED
INDICES ARE MARGINAL FOR THUNDERSTORMS OVER THE COASTAL WATERS. THE
LAND AREAS ARE COOL ENOUGH SO THAT THUNDER IS UNLIKELY.

VERY STRONG ZONAL FLOW DEVELOPS ACROSS THE NE PACIFIC FRIDAY NIGHT
AND CONTINUES THROUGH THE WEEKEND. 300 MB ISOTACHS ARE IN THE
160-170KT RANGE. A STRONG WET WARM FRONT ASSOCIATED WITH THE 130KT
NOSE OF THE JET STREAK WILL MOVE ACROSS W WA ON SATURDAY. MODELS ARE
IN FAIR AGREEMENT WITH THE STRENGTH AND GENERAL TIMING OF THIS
FEATURE. THIS WARM FRONT SHOULD GENERATE WIND ADVISORY LEVEL WINDS
OVER THE COAST AND N INTERIOR AND HEAVY RAIN OVER THE COAST AND
MOUNTAINS.

ALTHOUGH THERE WILL BE 2-3 INCHES OF HEAVY RAIN DURING THE 24 HOUR
PERIOD FROM 12Z SATURDAY-12Z SUNDAY...SO FAR IT LOOKS LIKE PRIMARILY
THE SKOKOMISH RIVER MAY BE AT RISK FOR FLOODING.

SNOW LEVELS START OUT NEAR 3000 FEET ON SATURDAY...AND WILL RISE TO
5500 TO 7000 FEET BY SATURDAY NIGHT. THERE COULD BE ENOUGH SNOW IN
THE TRANSITION TO PRODUCE BORDERLINE SNOW ADVISORY AMOUNTS OVER MT
BAKER AND MT RAINIER AGAIN. KAM

.LONG TERM...ECMWF AND GFS SHOW STRONG ZONAL FLOW CONTINUING INTO
EARLY NEXT WEEK WITH A BROAD FLAT UPPER LEVEL RIDGE OVER THE REGION.
LOTS OF FLOW THROUGH THE RIDGE WILL KEEP THIS A GENERALLY WET AND
BREEZY PERIOD THROUGH SUNDAY. THE MAIN PROBLEM WILL REMAIN HEAVY
RAIN SATURDAY NIGHT. FAIRLY STRONG WESTERLY 850 MB FLOW WILL REMAIN
30-45KT SATURDAY NIGHT INTO SUNDAY MORNING...THEN GRADUALLY DIMINISH
OVER THE NORTH AND CENTRAL PART OF W WA SUNDAY AFTERNOON. STRONGER W
FLOW WILL CONTINUE OVER NW OREGON AND THE SOUTHERN WA CASCADES.
THERE COULD BE ANOTHER 2-3 INCHES OF QPF OVER THE CENTRAL CASCADES
12Z SUNDAY THROUGH 12Z MONDAY WHICH COULD BRING SOME CASCADE RIVERS
CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH FRIDAY NIGHT. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. A
STRONG WARM FRONT WILL CROSS THE AREA SATURDAY WITH STRONG S FLOW
OVER THE OLYMPICS BECOMING W BY LATE AFTERNOON. THE STRONG W FLOW
WILL REACH THE CASCADES SATURDAY NIGHT. 2-3 INCHES OF RAIN ARE
EXPECTED OVER THE OLYMPICS AND PARTS OF THE CASCADES DURING THE 24
HOUR PERIOD FROM 12Z SATURDAY THROUGH 12Z SUNDAY. THIS COULD CAUSE
ANOTHER ROUND OF FLOODING ON THE SKOKOMISH RIVER AND PRIME SOME OF
THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH IS MOVING EAST OF THE CASCADES
EARLY THIS MORNING WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS IS
MOIST AND STABLE WITH WEAK SURFACE GRADIENTS. A COLD FRONT ABOUT 500
NM WEST OF SEATTLE AT 09Z WILL PUSH INTO THE REGION THIS EVENING
WITH STRONG SOUTHWEST FLOW ALOFT.

AREAS OF LIGHT RAIN REMAIN ACROSS THE REGION THIS MORNING WITH
WIDESPREAD LOW MVFR AND AREAS OF IFR. SOME TEMPORARY IMPROVEMENT TO
VFR IS POSSIBLE MIDDAY TODAY AS A TRANSITORY UPPER RIDGE MOVES OVER
THE AREA AND SURFACE GRADIENTS BECOME INCREASINGLY OFFSHORE.
WIDESPREAD RAIN WILL RAPIDLY SPREAD BACK INTO THE AREA BY EARLY
EVENING AHEAD OF THE NEXT FRONT WITH CEILINGS FALLING BACK TO MVFR.

KSEA...LOW MVFR AND TEMPO IFR CEILINGS EXPECTED THIS MORNING WITH
LIGHT RAIN SHOWERS AND SURFACE VSBYS OF 3-5SM AT TIMES. VFR CEILINGS
AT OR ABOVE 5K FEET POSSIBLE 18Z-00Z BUT WILL DROP AGAIN WITH MORE
RAIN THIS EVENING. LIGHT SOUTH-SOUTHEAST WIND THIS
MORNING...BECOMING SOUTHEAST 7 TO 12 KNOTS IN THE AFTERNOON AND
EVENING. 27

&&

.MARINE...A FRONT ASSOCIATED WITH A 970-975 MB LOW WELL WEST OF
HAIDA GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN
INLAND TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER
THE COASTAL WATERS MIDDAY TODAY THROUGH THIS EVENING WITH SMALL
CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. SOME MESOSCALE MODELS INDICATE A BRIEF
PERIOD OF GALE FORCE WIND POSSIBLE AT THE EAST ENTRANCE TO THE
STRAIT AND THE VICINITY OF THE SAN JUANS THIS EVENING JUST AHEAD OF
THE FRONT. INCREASING SOUTHERLY GRADIENT BEHIND THE FRONT WILL BRING
SMALL CRAFT ADVISORY WINDS TO PUGET SOUND AND HOOD CANAL TONIGHT. A
LONG PERIOD SWELL NEAR 22 FEET IS STILL EXPECTED ON THE COAST LATE
FRIDAY AFTERNOON OR FRIDAY NIGHT. TIDAL ANOMALIES ALONG THE COAST
ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH TIDE OCCURS SATURDAY
MORNING. IF SWELL REMAINS HIGH INTO SATURDAY MORNING AS CURRENTLY
EXPECTED...SOME COASTAL FLOODING IS POSSIBLE. ANOTHER STRONG FRONT
WILL ARRIVE ON SATURDAY WITH GALE FORCE WINDS ONCE AGAIN LIKELY OVER
THE COASTAL WATERS...THE NORTHERN INLAND WATERS...AND THE STRAIT
ENTRANCES. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML









000
FXUS66 KSEW 181102
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
302 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...A FRONTAL SYSTEM OFFSHORE APPROACHING 130W WILL BRING
A CHANCE OF RAIN TODAY...AND WILL SPREAD MORE CONTINUOUS RAIN OVER
THE AREA LATER THIS AFTERNOON. THE COLD FRONT DOES NOT LOOK ALL THAT
STRONG ON IR IMAGERY SO CHANCE POPS LOOK FINE FOR THIS MORNING AND
PROBABLY MUCH OF THE AFTERNOON. THE WETTEST PERIOD WILL BE TONIGHT
AS THE COLD FRONT CROSSES W WA. SNOW LEVELS ARE JUST LOW ENOUGH SO
THAT THE HIGHER ROADS TO MT BAKER AND MT RAINIER MAY RECEIVE
BORDERLINE SNOW ADVISORY AMOUNTS. STEVENS PASS MAY GET A FEW INCHES
OF SNOW LATE TONIGHT BUT SNOQUALMIE WILL PROBABLY JUST SEE RAIN.

THE TRAILING UPPER LEVEL TROUGH NEAR 140W-145W AT 09Z WILL CROSS W
WA ON FRIDAY. IR IMAGERY SHOWS THE AIR MASS IN THE TROUGH TO BE
NICELY UNSTABLE...WHICH WILL BE GOOD FOR SHOWER DEVELOPMENT AS IT
MOVES INLAND. LIKELY POPS FOR FRIDAY MORNING DECREASING TO CHANCE
POPS IN THE AFTERNOON AS THE TROUGH MOVES EAST LOOK FINE. LIFTED
INDICES ARE MARGINAL FOR THUNDERSTORMS OVER THE COASTAL WATERS. THE
LAND AREAS ARE COOL ENOUGH SO THAT THUNDER IS UNLIKELY.

VERY STRONG ZONAL FLOW DEVELOPS ACROSS THE NE PACIFIC FRIDAY NIGHT
AND CONTINUES THROUGH THE WEEKEND. 300 MB ISOTACHS ARE IN THE
160-170KT RANGE. A STRONG WET WARM FRONT ASSOCIATED WITH THE 130KT
NOSE OF THE JET STREAK WILL MOVE ACROSS W WA ON SATURDAY. MODELS ARE
IN FAIR AGREEMENT WITH THE STRENGTH AND GENERAL TIMING OF THIS
FEATURE. THIS WARM FRONT SHOULD GENERATE WIND ADVISORY LEVEL WINDS
OVER THE COAST AND N INTERIOR AND HEAVY RAIN OVER THE COAST AND
MOUNTAINS.

ALTHOUGH THERE WILL BE 2-3 INCHES OF HEAVY RAIN DURING THE 24 HOUR
PERIOD FROM 12Z SATURDAY-12Z SUNDAY...SO FAR IT LOOKS LIKE PRIMARILY
THE SKOKOMISH RIVER MAY BE AT RISK FOR FLOODING.

SNOW LEVELS START OUT NEAR 3000 FEET ON SATURDAY...AND WILL RISE TO
5500 TO 7000 FEET BY SATURDAY NIGHT. THERE COULD BE ENOUGH SNOW IN
THE TRANSITION TO PRODUCE BORDERLINE SNOW ADVISORY AMOUNTS OVER MT
BAKER AND MT RAINIER AGAIN. KAM

.LONG TERM...ECMWF AND GFS SHOW STRONG ZONAL FLOW CONTINUING INTO
EARLY NEXT WEEK WITH A BROAD FLAT UPPER LEVEL RIDGE OVER THE REGION.
LOTS OF FLOW THROUGH THE RIDGE WILL KEEP THIS A GENERALLY WET AND
BREEZY PERIOD THROUGH SUNDAY. THE MAIN PROBLEM WILL REMAIN HEAVY
RAIN SATURDAY NIGHT. FAIRLY STRONG WESTERLY 850 MB FLOW WILL REMAIN
30-45KT SATURDAY NIGHT INTO SUNDAY MORNING...THEN GRADUALLY DIMINISH
OVER THE NORTH AND CENTRAL PART OF W WA SUNDAY AFTERNOON. STRONGER W
FLOW WILL CONTINUE OVER NW OREGON AND THE SOUTHERN WA CASCADES.
THERE COULD BE ANOTHER 2-3 INCHES OF QPF OVER THE CENTRAL CASCADES
12Z SUNDAY THROUGH 12Z MONDAY WHICH COULD BRING SOME CASCADE RIVERS
CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH FRIDAY NIGHT. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. A
STRONG WARM FRONT WILL CROSS THE AREA SATURDAY WITH STRONG S FLOW
OVER THE OLYMPICS BECOMING W BY LATE AFTERNOON. THE STRONG W FLOW
WILL REACH THE CASCADES SATURDAY NIGHT. 2-3 INCHES OF RAIN ARE
EXPECTED OVER THE OLYMPICS AND PARTS OF THE CASCADES DURING THE 24
HOUR PERIOD FROM 12Z SATURDAY THROUGH 12Z SUNDAY. THIS COULD CAUSE
ANOTHER ROUND OF FLOODING ON THE SKOKOMISH RIVER AND PRIME SOME OF
THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH IS MOVING EAST OF THE CASCADES
EARLY THIS MORNING WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS IS
MOIST AND STABLE WITH WEAK SURFACE GRADIENTS. A COLD FRONT ABOUT 500
NM WEST OF SEATTLE AT 09Z WILL PUSH INTO THE REGION THIS EVENING
WITH STRONG SOUTHWEST FLOW ALOFT.

AREAS OF LIGHT RAIN REMAIN ACROSS THE REGION THIS MORNING WITH
WIDESPREAD LOW MVFR AND AREAS OF IFR. SOME TEMPORARY IMPROVEMENT TO
VFR IS POSSIBLE MIDDAY TODAY AS A TRANSITORY UPPER RIDGE MOVES OVER
THE AREA AND SURFACE GRADIENTS BECOME INCREASINGLY OFFSHORE.
WIDESPREAD RAIN WILL RAPIDLY SPREAD BACK INTO THE AREA BY EARLY
EVENING AHEAD OF THE NEXT FRONT WITH CEILINGS FALLING BACK TO MVFR.

KSEA...LOW MVFR AND TEMPO IFR CEILINGS EXPECTED THIS MORNING WITH
LIGHT RAIN SHOWERS AND SURFACE VSBYS OF 3-5SM AT TIMES. VFR CEILINGS
AT OR ABOVE 5K FEET POSSIBLE 18Z-00Z BUT WILL DROP AGAIN WITH MORE
RAIN THIS EVENING. LIGHT SOUTH-SOUTHEAST WIND THIS
MORNING...BECOMING SOUTHEAST 7 TO 12 KNOTS IN THE AFTERNOON AND
EVENING. 27

&&

.MARINE...A FRONT ASSOCIATED WITH A 970-975 MB LOW WELL WEST OF
HAIDA GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN
INLAND TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER
THE COASTAL WATERS MIDDAY TODAY THROUGH THIS EVENING WITH SMALL
CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. SOME MESOSCALE MODELS INDICATE A BRIEF
PERIOD OF GALE FORCE WIND POSSIBLE AT THE EAST ENTRANCE TO THE
STRAIT AND THE VICINITY OF THE SAN JUANS THIS EVENING JUST AHEAD OF
THE FRONT. INCREASING SOUTHERLY GRADIENT BEHIND THE FRONT WILL BRING
SMALL CRAFT ADVISORY WINDS TO PUGET SOUND AND HOOD CANAL TONIGHT. A
LONG PERIOD SWELL NEAR 22 FEET IS STILL EXPECTED ON THE COAST LATE
FRIDAY AFTERNOON OR FRIDAY NIGHT. TIDAL ANOMALIES ALONG THE COAST
ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH TIDE OCCURS SATURDAY
MORNING. IF SWELL REMAINS HIGH INTO SATURDAY MORNING AS CURRENTLY
EXPECTED...SOME COASTAL FLOODING IS POSSIBLE. ANOTHER STRONG FRONT
WILL ARRIVE ON SATURDAY WITH GALE FORCE WINDS ONCE AGAIN LIKELY OVER
THE COASTAL WATERS...THE NORTHERN INLAND WATERS...AND THE STRAIT
ENTRANCES. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML









000
FXUS66 KSEW 181102
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
302 AM PST THU DEC 18 2014

.SYNOPSIS...AN APPROACHING FRONTAL SYSTEM WILL BRING A CHANCE OF
RAIN TODAY...FOLLOWED BY MORE CONTINUOUS RAIN TONIGHT AS THE COLD
FRONT MOVES INLAND. AN UPPER LEVEL TROUGH WILL BRING SCATTERED
SHOWERS ON FRIDAY. STRONG MOIST WEST FLOW ALOFT OVER THE NORTHEAST
PACIFIC WILL BRING A WINDY AND RAINY PATTERN THIS WEEKEND. A BROAD
UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION EARLY NEXT WEEK FOR
NOT QUITE AS WET WEATHER.

&&

.SHORT TERM...A FRONTAL SYSTEM OFFSHORE APPROACHING 130W WILL BRING
A CHANCE OF RAIN TODAY...AND WILL SPREAD MORE CONTINUOUS RAIN OVER
THE AREA LATER THIS AFTERNOON. THE COLD FRONT DOES NOT LOOK ALL THAT
STRONG ON IR IMAGERY SO CHANCE POPS LOOK FINE FOR THIS MORNING AND
PROBABLY MUCH OF THE AFTERNOON. THE WETTEST PERIOD WILL BE TONIGHT
AS THE COLD FRONT CROSSES W WA. SNOW LEVELS ARE JUST LOW ENOUGH SO
THAT THE HIGHER ROADS TO MT BAKER AND MT RAINIER MAY RECEIVE
BORDERLINE SNOW ADVISORY AMOUNTS. STEVENS PASS MAY GET A FEW INCHES
OF SNOW LATE TONIGHT BUT SNOQUALMIE WILL PROBABLY JUST SEE RAIN.

THE TRAILING UPPER LEVEL TROUGH NEAR 140W-145W AT 09Z WILL CROSS W
WA ON FRIDAY. IR IMAGERY SHOWS THE AIR MASS IN THE TROUGH TO BE
NICELY UNSTABLE...WHICH WILL BE GOOD FOR SHOWER DEVELOPMENT AS IT
MOVES INLAND. LIKELY POPS FOR FRIDAY MORNING DECREASING TO CHANCE
POPS IN THE AFTERNOON AS THE TROUGH MOVES EAST LOOK FINE. LIFTED
INDICES ARE MARGINAL FOR THUNDERSTORMS OVER THE COASTAL WATERS. THE
LAND AREAS ARE COOL ENOUGH SO THAT THUNDER IS UNLIKELY.

VERY STRONG ZONAL FLOW DEVELOPS ACROSS THE NE PACIFIC FRIDAY NIGHT
AND CONTINUES THROUGH THE WEEKEND. 300 MB ISOTACHS ARE IN THE
160-170KT RANGE. A STRONG WET WARM FRONT ASSOCIATED WITH THE 130KT
NOSE OF THE JET STREAK WILL MOVE ACROSS W WA ON SATURDAY. MODELS ARE
IN FAIR AGREEMENT WITH THE STRENGTH AND GENERAL TIMING OF THIS
FEATURE. THIS WARM FRONT SHOULD GENERATE WIND ADVISORY LEVEL WINDS
OVER THE COAST AND N INTERIOR AND HEAVY RAIN OVER THE COAST AND
MOUNTAINS.

ALTHOUGH THERE WILL BE 2-3 INCHES OF HEAVY RAIN DURING THE 24 HOUR
PERIOD FROM 12Z SATURDAY-12Z SUNDAY...SO FAR IT LOOKS LIKE PRIMARILY
THE SKOKOMISH RIVER MAY BE AT RISK FOR FLOODING.

SNOW LEVELS START OUT NEAR 3000 FEET ON SATURDAY...AND WILL RISE TO
5500 TO 7000 FEET BY SATURDAY NIGHT. THERE COULD BE ENOUGH SNOW IN
THE TRANSITION TO PRODUCE BORDERLINE SNOW ADVISORY AMOUNTS OVER MT
BAKER AND MT RAINIER AGAIN. KAM

.LONG TERM...ECMWF AND GFS SHOW STRONG ZONAL FLOW CONTINUING INTO
EARLY NEXT WEEK WITH A BROAD FLAT UPPER LEVEL RIDGE OVER THE REGION.
LOTS OF FLOW THROUGH THE RIDGE WILL KEEP THIS A GENERALLY WET AND
BREEZY PERIOD THROUGH SUNDAY. THE MAIN PROBLEM WILL REMAIN HEAVY
RAIN SATURDAY NIGHT. FAIRLY STRONG WESTERLY 850 MB FLOW WILL REMAIN
30-45KT SATURDAY NIGHT INTO SUNDAY MORNING...THEN GRADUALLY DIMINISH
OVER THE NORTH AND CENTRAL PART OF W WA SUNDAY AFTERNOON. STRONGER W
FLOW WILL CONTINUE OVER NW OREGON AND THE SOUTHERN WA CASCADES.
THERE COULD BE ANOTHER 2-3 INCHES OF QPF OVER THE CENTRAL CASCADES
12Z SUNDAY THROUGH 12Z MONDAY WHICH COULD BRING SOME CASCADE RIVERS
CLOSE TO FLOOD STAGE.

THE BROAD FLAT RIDGE MAINTAINS STRONG SOMEWHAT MOIST W FLOW ALOFT
OVER THE AREA MONDAY AND TUESDAY...BUT THE AIR MASS IS DRIER FOR
MUCH LESS RAIN. GFS/ECMWF BOTH BRING AN UPPER LEVEL SHORTWAVE TROUGH
ACROSS THE AREA ON WEDNESDAY...THEN DEVELOP COOL DRY N FLOW ALOFT
BEHIND IT FOR THURSDAY. WE WILL SEE IF THIS MODEL AGREEMENT HOLDS.
KAM

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH FRIDAY NIGHT. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. A
STRONG WARM FRONT WILL CROSS THE AREA SATURDAY WITH STRONG S FLOW
OVER THE OLYMPICS BECOMING W BY LATE AFTERNOON. THE STRONG W FLOW
WILL REACH THE CASCADES SATURDAY NIGHT. 2-3 INCHES OF RAIN ARE
EXPECTED OVER THE OLYMPICS AND PARTS OF THE CASCADES DURING THE 24
HOUR PERIOD FROM 12Z SATURDAY THROUGH 12Z SUNDAY. THIS COULD CAUSE
ANOTHER ROUND OF FLOODING ON THE SKOKOMISH RIVER AND PRIME SOME OF
THE CASCADE RIVERS.

LOW LEVEL W FLOW ALOFT OVER W WA WILL DIMINISH SUNDAY AND SUNDAY
NIGHT AS THE CORE OF STRONGEST WINDS SLIDES DOWN OVER NW OREGON AND
THE SOUTHERN WA CASCADES. STILL...ANOTHER 2-3 INCHES OF RAIN COULD
FALL OVER THE CENTRAL CASCADES BETWEEN 12Z SUNDAY AND 12Z MONDAY.
THIS ADDED RAINFALL COULD PUSH SOME OF THE MORE FLOOD PRONE CASCADE
RIVERS CLOSE TO FLOOD STAGE. KAM

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH IS MOVING EAST OF THE CASCADES
EARLY THIS MORNING WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS IS
MOIST AND STABLE WITH WEAK SURFACE GRADIENTS. A COLD FRONT ABOUT 500
NM WEST OF SEATTLE AT 09Z WILL PUSH INTO THE REGION THIS EVENING
WITH STRONG SOUTHWEST FLOW ALOFT.

AREAS OF LIGHT RAIN REMAIN ACROSS THE REGION THIS MORNING WITH
WIDESPREAD LOW MVFR AND AREAS OF IFR. SOME TEMPORARY IMPROVEMENT TO
VFR IS POSSIBLE MIDDAY TODAY AS A TRANSITORY UPPER RIDGE MOVES OVER
THE AREA AND SURFACE GRADIENTS BECOME INCREASINGLY OFFSHORE.
WIDESPREAD RAIN WILL RAPIDLY SPREAD BACK INTO THE AREA BY EARLY
EVENING AHEAD OF THE NEXT FRONT WITH CEILINGS FALLING BACK TO MVFR.

KSEA...LOW MVFR AND TEMPO IFR CEILINGS EXPECTED THIS MORNING WITH
LIGHT RAIN SHOWERS AND SURFACE VSBYS OF 3-5SM AT TIMES. VFR CEILINGS
AT OR ABOVE 5K FEET POSSIBLE 18Z-00Z BUT WILL DROP AGAIN WITH MORE
RAIN THIS EVENING. LIGHT SOUTH-SOUTHEAST WIND THIS
MORNING...BECOMING SOUTHEAST 7 TO 12 KNOTS IN THE AFTERNOON AND
EVENING. 27

&&

.MARINE...A FRONT ASSOCIATED WITH A 970-975 MB LOW WELL WEST OF
HAIDA GWAII WILL MOVE THROUGH THE OFFSHORE WATERS TODAY...THEN
INLAND TONIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER
THE COASTAL WATERS MIDDAY TODAY THROUGH THIS EVENING WITH SMALL
CRAFT ADVISORY CONDITIONS FOR THE STRAIT...NORTHERN INLAND
WATERS...AND ADMIRALTY INLET. SOME MESOSCALE MODELS INDICATE A BRIEF
PERIOD OF GALE FORCE WIND POSSIBLE AT THE EAST ENTRANCE TO THE
STRAIT AND THE VICINITY OF THE SAN JUANS THIS EVENING JUST AHEAD OF
THE FRONT. INCREASING SOUTHERLY GRADIENT BEHIND THE FRONT WILL BRING
SMALL CRAFT ADVISORY WINDS TO PUGET SOUND AND HOOD CANAL TONIGHT. A
LONG PERIOD SWELL NEAR 22 FEET IS STILL EXPECTED ON THE COAST LATE
FRIDAY AFTERNOON OR FRIDAY NIGHT. TIDAL ANOMALIES ALONG THE COAST
ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH TIDE OCCURS SATURDAY
MORNING. IF SWELL REMAINS HIGH INTO SATURDAY MORNING AS CURRENTLY
EXPECTED...SOME COASTAL FLOODING IS POSSIBLE. ANOTHER STRONG FRONT
WILL ARRIVE ON SATURDAY WITH GALE FORCE WINDS ONCE AGAIN LIKELY OVER
THE COASTAL WATERS...THE NORTHERN INLAND WATERS...AND THE STRAIT
ENTRANCES. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








000
FXUS66 KOTX 181024
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
223 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will Bbe stubborn in the
northern valleys, especially in the Cascade valleys where some
light to moderate snow is possible. Warming increases Saturday
night into Sunday, making it a mainly rain/high mountain snow
event by Sunday afternoon. In this transition, there is a small
chance of a wintry mix with pockets of freezing rain in a few of
the Cascade valleys. The 850mb 0C line pushes to the Canadian
border on Sunday. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. QPF looks juicy with a
0.25" to 0.40" possible from Saturday afternoon into Sunday
morning. Gusty winds will increase Saturday night into Sunday
evening with speeds 25-40 kts across the Columbia Basin. Gusty
winds will continue in the mountains through night, especially in
the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
06Z TAFS: A weak weather disturbance will generate light rain at
the KLWS, KPUW, KGEG, KSFF and KCOE TAF sites through early
Thursday morning. Cigs will deteriorate at most TAF locations
through Thursday morning with MVFR conditions expected at KEAT,
KMWH, KGEG, KSFF and KCOE. Drier easterly winds at KPUW and KLWS
are expected to keep these locations at VFR; however, confidence
of VFR conditions persisting at KPUW through Thursday morning is
low. Improving cigs is expected southeast to northwest across the
basin for Thursday afternoon as the next Pacific storm system
approaches and the easterly pressure gradient strengthens. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 181024
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
223 AM PST THU DEC 18 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...
Today through Friday night...A weak cold front and accompanying
trough is moving through the forecast early this morning and will
be followed by a weak ridge of high pressure today. Radar is
indicating rain and snow showers across the east and southeast
zones this morning as the front moves out of the area. Road
temperatures are warm enough that any snow that does fall should
melt. The exception will be over Lookout Pass where they could get
an inch or two through the early morning. Up-sloping flow will
keep rain and snow showers across the Panhandle through the day
with light accumulations expected, otherwise we should see a brief
break in the weather today. Expect areas of fog and stratus to
linger over the lower elevations and northern valleys through the
morning.

As mentioned above the break will be brief as another wet weather
system will move in off the Pacific tonight and track across the
forecast area on Friday. Moisture is plentiful with PWAT`s rising
to almost 200 percent of normal. South-southeast lower level flow
overnight will overcome the shadow effect off the Cascades and all
areas will see measurable precipitation. The cold front will track
across the region during the day Friday and result in a drying
trend from West to east Friday afternoon.

This same southerly flow will allow warm air to rapidly advect
into the region through the night. So we are expecting mainly
valley rain and mountain snow. The challenge is the cooler air in
the Cascade valleys...chiefly the Methow valley and the Okanogan
valley. Model guidance has been to cool in these valleys the past
few days and it looks like the 00z runs are following that trend.
That does not mean that these valleys will not see snow, just
possibly not as much as expected. This could easily result in a
busted forecast for these valleys. For now it looks like the
Methow valley will pick up 1-3 inches of snow. The current models
sure want to scour out the remainder of the valleys and the
Waterville Plateau as the warm air move through the area. These
areas could still pick up 1-2 inches above 1500-2000 feet before
turning over to rain. For the mountains 2-5 inches are likely with
a few inches more up near the crest of the Cascades. For the
Wenatchee valley and along the Columbia river across to Spokane
and Coeur D`Alene the precipitation could start as wet snow or a
rain/snow mix before turning over to all rain through the night.

Some showers will linger across the Cascade crest and up-sloping
into the Panhandle will keep a pretty good chance of rain and snow
showers Friday night. Otherwise expect drier conditions for the
remainder of the forecast area. Tobin

Saturday through Sunday night...One very wet period. An atmospheric
river will take aim on the Pacific NW. The GFS and ECMWF show
agreement of moderate isentropic lift spreading across the region
Saturday morning with a stream of plentiful moisture for most of
the weekend. Pwats of over an inch pool off the coast with up to
0.75" of inch making it east of the Cascades. Again precipitation
type will be tricky. Snow levels will Bbe stubborn in the
northern valleys, especially in the Cascade valleys where some
light to moderate snow is possible. Warming increases Saturday
night into Sunday, making it a mainly rain/high mountain snow
event by Sunday afternoon. In this transition, there is a small
chance of a wintry mix with pockets of freezing rain in a few of
the Cascade valleys. The 850mb 0C line pushes to the Canadian
border on Sunday. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. QPF looks juicy with a
0.25" to 0.40" possible from Saturday afternoon into Sunday
morning. Gusty winds will increase Saturday night into Sunday
evening with speeds 25-40 kts across the Columbia Basin. Gusty
winds will continue in the mountains through night, especially in
the Cascades.

Monday through Wednesday...A cold front slides through the region
early Monday allowing the atmospheric river to sag southward and
cooler drier air to filter in from the north. The bulk of the
precipitation will continue to be found near the Cascade crest and
central Panhandle mountains through Monday through Monday evening
and then gradually taper off. A few lingering showers are possible
by early Monday morning across the northern mountains, but for the
most part partial clearing can be expected will allow temperatures
to cool late Monday night and into Tuesday. With the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. In the 00z model runs this feature looks to swing wide
and drops west and south of the region, with the main brunt of the
precipitation found across Oregon. Opted to continue a drier
forecast through mid week with the best chance of snow falling
near the Cascade crest, Blue mountains and central Panhandle
mountains. / rfox.

&&

.AVIATION...
06Z TAFS: A weak weather disturbance will generate light rain at
the KLWS, KPUW, KGEG, KSFF and KCOE TAF sites through early
Thursday morning. Cigs will deteriorate at most TAF locations
through Thursday morning with MVFR conditions expected at KEAT,
KMWH, KGEG, KSFF and KCOE. Drier easterly winds at KPUW and KLWS
are expected to keep these locations at VFR; however, confidence
of VFR conditions persisting at KPUW through Thursday morning is
low. Improving cigs is expected southeast to northwest across the
basin for Thursday afternoon as the next Pacific storm system
approaches and the easterly pressure gradient strengthens. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        40  36  40  32  39  37 /  30  40  90  10  80  90
Coeur d`Alene  40  34  40  32  39  37 /  60  20 100  20  70 100
Pullman        42  35  43  31  43  41 /  40  40  90  10  70  90
Lewiston       44  35  46  32  45  44 /  40  20  80  10  50  80
Colville       37  34  38  33  37  36 /  30  60 100  20  80 100
Sandpoint      37  34  37  32  37  36 /  60  40 100  30  60 100
Kellogg        38  32  37  30  37  35 /  70  30 100  40  50 100
Moses Lake     42  36  42  32  40  37 /  10  70  70  10  80  80
Wenatchee      39  33  40  31  38  32 /  10  80  50  10  90  80
Omak           38  33  37  30  35  32 /  20  90  80  10  80  90

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 180556
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
955 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.


&&

.DISCUSSION...
Another round of light precipitation is increasing across the
eastern half of the forecast area late this evening. A mix of rain
and snow can be expected between 2,000 and 2,300 feet across the
Northeast Mtns and in the Northern Panhandle. Around an inch of
snow is expected at lower elevations above 2,500 feet and up
around 2 inches for the mountains across this area. Snow levels
will be a bit higher at around 3,000 feet in the Central Panhandle
Mtns. The main impact for snow across these areas will be for
travelers over Lookout Pass with 1-2 inches of snow possible.
Temperatures will hover around freezing for these areas through
Thursday evening with a slick morning commute possible. /SVH


&&

.AVIATION...
06Z TAFS: A weak weather disturbance will generate light rain at
the KLWS, KPUW, KGEG, KSFF and KCOE TAF sites through early
Thursday morning. Cigs will deteriorate at most TAF locations
through Thursday morning with MVFR conditions expected at KEAT,
KMWH, KGEG, KSFF and KCOE. Drier easterly winds at KPUW and KLWS
are expected to keep these locations at VFR; however, confidence
of VFR conditions persisting at KPUW through Thursday morning is
low. Improving cigs is expected southeast to northwest across the
basin for Thursday afternoon as the next Pacific storm system
approaches and the easterly pressure gradient strengthens. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        33  40  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  40  32  39  32  39 /  50  60  20 100  20  70
Pullman        35  44  34  42  32  43 /  50  40  40  90  10  70
Lewiston       38  46  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  50  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     34  39  36  42  30  39 /  10  10  70  70  10  70
Wenatchee      33  38  33  40  30  34 /  10  10  70  60  10  70
Omak           30  35  32  37  30  33 /  20  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 180556
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
955 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.


&&

.DISCUSSION...
Another round of light precipitation is increasing across the
eastern half of the forecast area late this evening. A mix of rain
and snow can be expected between 2,000 and 2,300 feet across the
Northeast Mtns and in the Northern Panhandle. Around an inch of
snow is expected at lower elevations above 2,500 feet and up
around 2 inches for the mountains across this area. Snow levels
will be a bit higher at around 3,000 feet in the Central Panhandle
Mtns. The main impact for snow across these areas will be for
travelers over Lookout Pass with 1-2 inches of snow possible.
Temperatures will hover around freezing for these areas through
Thursday evening with a slick morning commute possible. /SVH


&&

.AVIATION...
06Z TAFS: A weak weather disturbance will generate light rain at
the KLWS, KPUW, KGEG, KSFF and KCOE TAF sites through early
Thursday morning. Cigs will deteriorate at most TAF locations
through Thursday morning with MVFR conditions expected at KEAT,
KMWH, KGEG, KSFF and KCOE. Drier easterly winds at KPUW and KLWS
are expected to keep these locations at VFR; however, confidence
of VFR conditions persisting at KPUW through Thursday morning is
low. Improving cigs is expected southeast to northwest across the
basin for Thursday afternoon as the next Pacific storm system
approaches and the easterly pressure gradient strengthens. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        33  40  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  40  32  39  32  39 /  50  60  20 100  20  70
Pullman        35  44  34  42  32  43 /  50  40  40  90  10  70
Lewiston       38  46  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  50  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     34  39  36  42  30  39 /  10  10  70  70  10  70
Wenatchee      33  38  33  40  30  34 /  10  10  70  60  10  70
Omak           30  35  32  37  30  33 /  20  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 180556
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
955 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.


&&

.DISCUSSION...
Another round of light precipitation is increasing across the
eastern half of the forecast area late this evening. A mix of rain
and snow can be expected between 2,000 and 2,300 feet across the
Northeast Mtns and in the Northern Panhandle. Around an inch of
snow is expected at lower elevations above 2,500 feet and up
around 2 inches for the mountains across this area. Snow levels
will be a bit higher at around 3,000 feet in the Central Panhandle
Mtns. The main impact for snow across these areas will be for
travelers over Lookout Pass with 1-2 inches of snow possible.
Temperatures will hover around freezing for these areas through
Thursday evening with a slick morning commute possible. /SVH


&&

.AVIATION...
06Z TAFS: A weak weather disturbance will generate light rain at
the KLWS, KPUW, KGEG, KSFF and KCOE TAF sites through early
Thursday morning. Cigs will deteriorate at most TAF locations
through Thursday morning with MVFR conditions expected at KEAT,
KMWH, KGEG, KSFF and KCOE. Drier easterly winds at KPUW and KLWS
are expected to keep these locations at VFR; however, confidence
of VFR conditions persisting at KPUW through Thursday morning is
low. Improving cigs is expected southeast to northwest across the
basin for Thursday afternoon as the next Pacific storm system
approaches and the easterly pressure gradient strengthens. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        33  40  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  40  32  39  32  39 /  50  60  20 100  20  70
Pullman        35  44  34  42  32  43 /  50  40  40  90  10  70
Lewiston       38  46  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  50  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     34  39  36  42  30  39 /  10  10  70  70  10  70
Wenatchee      33  38  33  40  30  34 /  10  10  70  60  10  70
Omak           30  35  32  37  30  33 /  20  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 180556
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
955 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.


&&

.DISCUSSION...
Another round of light precipitation is increasing across the
eastern half of the forecast area late this evening. A mix of rain
and snow can be expected between 2,000 and 2,300 feet across the
Northeast Mtns and in the Northern Panhandle. Around an inch of
snow is expected at lower elevations above 2,500 feet and up
around 2 inches for the mountains across this area. Snow levels
will be a bit higher at around 3,000 feet in the Central Panhandle
Mtns. The main impact for snow across these areas will be for
travelers over Lookout Pass with 1-2 inches of snow possible.
Temperatures will hover around freezing for these areas through
Thursday evening with a slick morning commute possible. /SVH


&&

.AVIATION...
06Z TAFS: A weak weather disturbance will generate light rain at
the KLWS, KPUW, KGEG, KSFF and KCOE TAF sites through early
Thursday morning. Cigs will deteriorate at most TAF locations
through Thursday morning with MVFR conditions expected at KEAT,
KMWH, KGEG, KSFF and KCOE. Drier easterly winds at KPUW and KLWS
are expected to keep these locations at VFR; however, confidence
of VFR conditions persisting at KPUW through Thursday morning is
low. Improving cigs is expected southeast to northwest across the
basin for Thursday afternoon as the next Pacific storm system
approaches and the easterly pressure gradient strengthens. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        33  40  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  40  32  39  32  39 /  50  60  20 100  20  70
Pullman        35  44  34  42  32  43 /  50  40  40  90  10  70
Lewiston       38  46  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  50  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     34  39  36  42  30  39 /  10  10  70  70  10  70
Wenatchee      33  38  33  40  30  34 /  10  10  70  60  10  70
Omak           30  35  32  37  30  33 /  20  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KPQR 180536
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
934 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE CONTINUES TO BRING AREAS OF LIGHT RAIN
AND CASCADE SNOW TO THE DISTRICT THIS EVENING. EXPECT PRECIPITATION
TO BECOME MORE SPOTTY OVERNIGHT AS THE LOW DECAYS. LINGERING MOISTURE
SHOULD ALLOW PATCHY FOG TO DEVELOP OVERNIGHT. RAIN WILL REDEVELOP BY
LATE THURSDAY AND INCREASE OVERNIGHT AS A MORE ORGANIZED FRONTAL
SYSTEM MOVES ONSHORE. THIS FRONT WILL ALSO BRING A PERIOD OF WINDY
CONDITIONS TO THE COAST THURSDAY AFTERNOON AND EVENING. RAIN WILL
TAPER TO SHOWERS BEHIND THE COLD FRONT FRIDAY.SNOW LEVELS WILL RISE
ABOVE THE CASCADE PASSES AHEAD OF THIS FRONT...THEN FALL BACK BELOW
PASS LEVEL WITH SOME ACCUMULATING SNOW SHOWERS FRIDAY AND FRIDAY
NIGHT. MILD AND VERY WET WEATHER IS EXPECTED THIS WEEKEND. THERE IS
POTENTIAL FOR AN ATMOSPHERIC RIVER AND ASSOCIATED HEAVY RAIN TO
DEVELOP OVER THE AREA...WITH SOME FLOODING POSSIBLE LATER THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...WEAK LOW PRESSURE CAN BE
SEEN ON NWS DOPPLER RADAR MOVING NORTHEASTWARD INTO SW WASHINGTON
THIS EVENING...WITH A VERY LOOSE CIRCULATION MOVING ACROSS THE
WILLAPA HILLS. THIS SYSTEM IS DECAYING...AND AS A RESULT THE AREAL
COVERAGE OF LIGHT RAIN AND CASCADE SNOW IS DECREASING THIS EVENING.
THAT SAID...THE AIR MASS REMAINS VERY MOIST AND FLOW REMAINS WEAKLY
CYCLONIC UP TO 700 MB. THEREFORE IT WOULD NOT BE SURPRISING TO SEE
AREAS OF -RA CONTINUE ACROSS OUR FORECAST AREA OVERNIGHT AND INTO
THURSDAY. ALSO...THE 00Z NAM/GFS KEY IN ON ANOTHER WEAK LOW OFF THE
SRN OREGON COAST WHICH IS BRINGING A BIT MORE LIGHT RAIN TO SW OREGON
THIS EVENING. THIS LOW IS EXPECTED TO LIFT N-NE AND DECAY WHILE
MOVING ACROSS OUR FORECAST AREA THURSDAY...BUT COULD HOLD TOGETHER
ENOUGH TO BRING SOME PERIODS OF LIGHT RAIN THROUGH THE DAY. KEEPING
THIS IN MIND...WE INCREASED POPS THROUGH THURSDAY...BUT QPF WILL BE
VERY LIGHT.

ATTENTION THEN TURNS TO THE NEXT MUCH STRONGER SYSTEM...PRESENTLY
PUSHING A COLD FRONT ACROSS 140W. THIS SYSTEM WILL BE A FAST
MOVER...LIKELY STARTING TO SPREAD MORE SIGNIFICANT RAIN ONSHORE BY
LATE THURSDAY AFTERNOON. 00Z NAM/GFS SUGGEST THE NORTH AND CENTRAL
OREGON COAST GET INTO THE WARM SECTOR AHEAD OF THE COLD FRONT...
OPENING THE DOOR FOR STRONGER WINDS TO SURFACE AT LEAST AT THE
BEACHES AND HEADLANDS THURSDAY AFTERNOON AND EVENING. GRADIENTS
APPEAR TO REMAIN EASTERLY ENOUGH TO KEEP THE STRONGEST WINDS OUT OF
THE COASTAL COMMUNITIES...BUT THE 00Z NAM AND 4KM UW WRFGFS HAVE BEEN
TRENDING STRONGER WITH THE COASTAL JET AHEAD OF THE FRONT. THE 00Z
NAM SHOWS 950 MB WINDS UP TO 60 KT WITHIN THE COASTAL JET. DECIDED
EARLIER IN THE SHIFT TO ISSUE A HIGH WIND WATCH FOR THE BEACHES AND
HEADLANDS BASED ON THE 00Z NAM DATA...AND WITH THE UW WRFGFS TRENDING
STRONGER WE FEEL EVEN MORE CONFIDENT ABOUT THAT DECISION. THIS WILL
MAINLY BE AN ISSUE FOR TRAVELERS ALONG EXPOSED AREAS OF COASTAL
ROUTES...WHILE MOST COASTAL COMMUNITIES WILL LIKELY JUST SEE A BRIEF
1-3 HR PERIOD OF 40-45 MPH GUSTS.

MADE VERY FEW CHANGES BEYOND THURSDAY NIGHT AS THE CURRENT FORECAST
LOOKS ON TRACK FOR A VERY WET AND OCCASIONALLY WINDY WEEKEND. 00Z NAM
AND GFS CERTAINLY HAVE NOT BACKED DOWN FROM THEIR EARLIER FORECASTS
FOCUSING AN ATMOSPHERIC RIVER SQUARELY ON SW WASHINGTON AND NW
OREGON...WITH FLOODING RAINS POSSIBLE. THE 00Z WRFGFS CONTINUES TO
PRODUCE VERY HEAVY QPF WITH UP TO 8-12 INCHES OF RAIN IN THE HIGHER
TERRAIN AND 2-4 INCHES IN THE WILLAMETTE VALLEY BY MONDAY...EVEN WITH
HEAVY RAIN SHADOWING. WILL NEED TO MONITOR THIS VERY CLOSELY OVER THE
NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING ON AREA
MAINSTEM RIVERS.  WEAGLE

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...A MOIST LOWER ATMOSPHERE...DECREASING WINDS AND
VARYING VFR CLOUD DECKS SCATTERED OVER THE FORECAST WILL RESULT IN
A MIX OF IFR TO VFR CONDITIONS ACROSS THE AREA OVERNIGHT. SUSPECT
SOME DETERIORATION AT MOST TAF SITES. AS THE NEXT COLD FRONT
APPROACHES THE AREA THURSDAY...EXPECT SOUTHEAST TO EAST WINDS TO
INCREASE AGAIN...AND CAUSE MOST SITES WITH FLIGHT RESTRICTIONS TO
TURN VFR. EXPECT A PERIOD OF HIGH END IFR TO MVFR AS THE COLD
FRONT PUSHES INTO THE COAST AROUND 03Z FRIDAY...AND LIKELY AFTER
06Z FRIDAY FOR INTERIOR TAF SITES.

KPDX AND APPROACHES...DUE TO AMPLE LOW LEVEL MOISTURE AND
DECREASING WINDS OVER THE NEXT FEW HOURS...SUSPECT SOME
DETERIORATION...BUT CONFIDENCE IN THE DETAILS IS LOW.
HOWEVER...INCREASING EAST WINDS THURSDAY MORNING SHOULD ALLOW
ANY FLIGHT RESTRICTIONS TO DISAPPEAR. THEREAFTER...EXPECT
PRIMARILY VFR CONDITIONS THROUGH 06Z FRIDAY AS EAST WINDS CONTINUE
AHEAD OF A MODEST COLD FRONT. /NEUMAN

&&

.MARINE...SEAS CONTINUE TO HOVER NEAR 10 FT SO A SMALL CRAFT FOR
HAZARDOUS SEAS WAS EXTENDED THROUGH 4 AM...ALTHOUGH SEAS SHOULD
DROP SOLIDLY BELOW THIS HEIGHT WELL BEFORE THIS TIME. A MORE
ORGANIZED FRONTAL STORM SYSTEM WILL CAUSE IN WINDS TO INCREASE
ACROSS THE WATERS ON THURSDAY...PARTICULARLY OVER THE OUTER
WATERS. EVENTUALLY...THE FRONT WILL PUSH INTO THE WATERS DURING
THE EVENING AND PRODUCE A 3 TO 6 HOUR PERIOD OF GALE FORCE WIND
GUSTS OF 40 TO 45 KT ACROSS THE WATERS. SEAS SHOULD RESPOND
ACCORDINGLY AND RISE INTO AT LEAST THE MID TEENS. EXPECT SEAS TO
SUBSIDE FAIRLY QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE
THURSDAY NIGHT INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER
WAVE HEIGHTS WILL BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD
WESTERLY SWELL WILL LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY
EVENING. WAVE HEIGHTS MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS
COULD CERTAINLY CATCH OFF GUARD ANY UNINFORMED MARINERS THAT
VENTURE OUT FRIDAY MORNING. CONFIDENCE IS RELATIVELY HIGH THAT THIS
SWELL WILL LIKELY EXCEED 20 FT. IN FACT...THESE PATTERNS OFTEN
PRODUCE HIGHER SEAS THAN FORECASTED BY THE ENP WAVE MODEL. A HIGH
SURF ADVISORY APPEARS LIKELY. THE GOOD NEWS IS THAT THE LARGEST
SWELL WILL LIKELY ARRIVE DURING LOW TIDE AND DURING THE NIGHT TIME
HOURS WHEN MOST MARINERS AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
     EVENING FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM
     PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.



000
FXUS66 KPQR 180536
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
934 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE CONTINUES TO BRING AREAS OF LIGHT RAIN
AND CASCADE SNOW TO THE DISTRICT THIS EVENING. EXPECT PRECIPITATION
TO BECOME MORE SPOTTY OVERNIGHT AS THE LOW DECAYS. LINGERING MOISTURE
SHOULD ALLOW PATCHY FOG TO DEVELOP OVERNIGHT. RAIN WILL REDEVELOP BY
LATE THURSDAY AND INCREASE OVERNIGHT AS A MORE ORGANIZED FRONTAL
SYSTEM MOVES ONSHORE. THIS FRONT WILL ALSO BRING A PERIOD OF WINDY
CONDITIONS TO THE COAST THURSDAY AFTERNOON AND EVENING. RAIN WILL
TAPER TO SHOWERS BEHIND THE COLD FRONT FRIDAY.SNOW LEVELS WILL RISE
ABOVE THE CASCADE PASSES AHEAD OF THIS FRONT...THEN FALL BACK BELOW
PASS LEVEL WITH SOME ACCUMULATING SNOW SHOWERS FRIDAY AND FRIDAY
NIGHT. MILD AND VERY WET WEATHER IS EXPECTED THIS WEEKEND. THERE IS
POTENTIAL FOR AN ATMOSPHERIC RIVER AND ASSOCIATED HEAVY RAIN TO
DEVELOP OVER THE AREA...WITH SOME FLOODING POSSIBLE LATER THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...WEAK LOW PRESSURE CAN BE
SEEN ON NWS DOPPLER RADAR MOVING NORTHEASTWARD INTO SW WASHINGTON
THIS EVENING...WITH A VERY LOOSE CIRCULATION MOVING ACROSS THE
WILLAPA HILLS. THIS SYSTEM IS DECAYING...AND AS A RESULT THE AREAL
COVERAGE OF LIGHT RAIN AND CASCADE SNOW IS DECREASING THIS EVENING.
THAT SAID...THE AIR MASS REMAINS VERY MOIST AND FLOW REMAINS WEAKLY
CYCLONIC UP TO 700 MB. THEREFORE IT WOULD NOT BE SURPRISING TO SEE
AREAS OF -RA CONTINUE ACROSS OUR FORECAST AREA OVERNIGHT AND INTO
THURSDAY. ALSO...THE 00Z NAM/GFS KEY IN ON ANOTHER WEAK LOW OFF THE
SRN OREGON COAST WHICH IS BRINGING A BIT MORE LIGHT RAIN TO SW OREGON
THIS EVENING. THIS LOW IS EXPECTED TO LIFT N-NE AND DECAY WHILE
MOVING ACROSS OUR FORECAST AREA THURSDAY...BUT COULD HOLD TOGETHER
ENOUGH TO BRING SOME PERIODS OF LIGHT RAIN THROUGH THE DAY. KEEPING
THIS IN MIND...WE INCREASED POPS THROUGH THURSDAY...BUT QPF WILL BE
VERY LIGHT.

ATTENTION THEN TURNS TO THE NEXT MUCH STRONGER SYSTEM...PRESENTLY
PUSHING A COLD FRONT ACROSS 140W. THIS SYSTEM WILL BE A FAST
MOVER...LIKELY STARTING TO SPREAD MORE SIGNIFICANT RAIN ONSHORE BY
LATE THURSDAY AFTERNOON. 00Z NAM/GFS SUGGEST THE NORTH AND CENTRAL
OREGON COAST GET INTO THE WARM SECTOR AHEAD OF THE COLD FRONT...
OPENING THE DOOR FOR STRONGER WINDS TO SURFACE AT LEAST AT THE
BEACHES AND HEADLANDS THURSDAY AFTERNOON AND EVENING. GRADIENTS
APPEAR TO REMAIN EASTERLY ENOUGH TO KEEP THE STRONGEST WINDS OUT OF
THE COASTAL COMMUNITIES...BUT THE 00Z NAM AND 4KM UW WRFGFS HAVE BEEN
TRENDING STRONGER WITH THE COASTAL JET AHEAD OF THE FRONT. THE 00Z
NAM SHOWS 950 MB WINDS UP TO 60 KT WITHIN THE COASTAL JET. DECIDED
EARLIER IN THE SHIFT TO ISSUE A HIGH WIND WATCH FOR THE BEACHES AND
HEADLANDS BASED ON THE 00Z NAM DATA...AND WITH THE UW WRFGFS TRENDING
STRONGER WE FEEL EVEN MORE CONFIDENT ABOUT THAT DECISION. THIS WILL
MAINLY BE AN ISSUE FOR TRAVELERS ALONG EXPOSED AREAS OF COASTAL
ROUTES...WHILE MOST COASTAL COMMUNITIES WILL LIKELY JUST SEE A BRIEF
1-3 HR PERIOD OF 40-45 MPH GUSTS.

MADE VERY FEW CHANGES BEYOND THURSDAY NIGHT AS THE CURRENT FORECAST
LOOKS ON TRACK FOR A VERY WET AND OCCASIONALLY WINDY WEEKEND. 00Z NAM
AND GFS CERTAINLY HAVE NOT BACKED DOWN FROM THEIR EARLIER FORECASTS
FOCUSING AN ATMOSPHERIC RIVER SQUARELY ON SW WASHINGTON AND NW
OREGON...WITH FLOODING RAINS POSSIBLE. THE 00Z WRFGFS CONTINUES TO
PRODUCE VERY HEAVY QPF WITH UP TO 8-12 INCHES OF RAIN IN THE HIGHER
TERRAIN AND 2-4 INCHES IN THE WILLAMETTE VALLEY BY MONDAY...EVEN WITH
HEAVY RAIN SHADOWING. WILL NEED TO MONITOR THIS VERY CLOSELY OVER THE
NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING ON AREA
MAINSTEM RIVERS.  WEAGLE

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...A MOIST LOWER ATMOSPHERE...DECREASING WINDS AND
VARYING VFR CLOUD DECKS SCATTERED OVER THE FORECAST WILL RESULT IN
A MIX OF IFR TO VFR CONDITIONS ACROSS THE AREA OVERNIGHT. SUSPECT
SOME DETERIORATION AT MOST TAF SITES. AS THE NEXT COLD FRONT
APPROACHES THE AREA THURSDAY...EXPECT SOUTHEAST TO EAST WINDS TO
INCREASE AGAIN...AND CAUSE MOST SITES WITH FLIGHT RESTRICTIONS TO
TURN VFR. EXPECT A PERIOD OF HIGH END IFR TO MVFR AS THE COLD
FRONT PUSHES INTO THE COAST AROUND 03Z FRIDAY...AND LIKELY AFTER
06Z FRIDAY FOR INTERIOR TAF SITES.

KPDX AND APPROACHES...DUE TO AMPLE LOW LEVEL MOISTURE AND
DECREASING WINDS OVER THE NEXT FEW HOURS...SUSPECT SOME
DETERIORATION...BUT CONFIDENCE IN THE DETAILS IS LOW.
HOWEVER...INCREASING EAST WINDS THURSDAY MORNING SHOULD ALLOW
ANY FLIGHT RESTRICTIONS TO DISAPPEAR. THEREAFTER...EXPECT
PRIMARILY VFR CONDITIONS THROUGH 06Z FRIDAY AS EAST WINDS CONTINUE
AHEAD OF A MODEST COLD FRONT. /NEUMAN

&&

.MARINE...SEAS CONTINUE TO HOVER NEAR 10 FT SO A SMALL CRAFT FOR
HAZARDOUS SEAS WAS EXTENDED THROUGH 4 AM...ALTHOUGH SEAS SHOULD
DROP SOLIDLY BELOW THIS HEIGHT WELL BEFORE THIS TIME. A MORE
ORGANIZED FRONTAL STORM SYSTEM WILL CAUSE IN WINDS TO INCREASE
ACROSS THE WATERS ON THURSDAY...PARTICULARLY OVER THE OUTER
WATERS. EVENTUALLY...THE FRONT WILL PUSH INTO THE WATERS DURING
THE EVENING AND PRODUCE A 3 TO 6 HOUR PERIOD OF GALE FORCE WIND
GUSTS OF 40 TO 45 KT ACROSS THE WATERS. SEAS SHOULD RESPOND
ACCORDINGLY AND RISE INTO AT LEAST THE MID TEENS. EXPECT SEAS TO
SUBSIDE FAIRLY QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE
THURSDAY NIGHT INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER
WAVE HEIGHTS WILL BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD
WESTERLY SWELL WILL LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY
EVENING. WAVE HEIGHTS MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS
COULD CERTAINLY CATCH OFF GUARD ANY UNINFORMED MARINERS THAT
VENTURE OUT FRIDAY MORNING. CONFIDENCE IS RELATIVELY HIGH THAT THIS
SWELL WILL LIKELY EXCEED 20 FT. IN FACT...THESE PATTERNS OFTEN
PRODUCE HIGHER SEAS THAN FORECASTED BY THE ENP WAVE MODEL. A HIGH
SURF ADVISORY APPEARS LIKELY. THE GOOD NEWS IS THAT THE LARGEST
SWELL WILL LIKELY ARRIVE DURING LOW TIDE AND DURING THE NIGHT TIME
HOURS WHEN MOST MARINERS AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
     EVENING FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM
     PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 180536
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
934 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE CONTINUES TO BRING AREAS OF LIGHT RAIN
AND CASCADE SNOW TO THE DISTRICT THIS EVENING. EXPECT PRECIPITATION
TO BECOME MORE SPOTTY OVERNIGHT AS THE LOW DECAYS. LINGERING MOISTURE
SHOULD ALLOW PATCHY FOG TO DEVELOP OVERNIGHT. RAIN WILL REDEVELOP BY
LATE THURSDAY AND INCREASE OVERNIGHT AS A MORE ORGANIZED FRONTAL
SYSTEM MOVES ONSHORE. THIS FRONT WILL ALSO BRING A PERIOD OF WINDY
CONDITIONS TO THE COAST THURSDAY AFTERNOON AND EVENING. RAIN WILL
TAPER TO SHOWERS BEHIND THE COLD FRONT FRIDAY.SNOW LEVELS WILL RISE
ABOVE THE CASCADE PASSES AHEAD OF THIS FRONT...THEN FALL BACK BELOW
PASS LEVEL WITH SOME ACCUMULATING SNOW SHOWERS FRIDAY AND FRIDAY
NIGHT. MILD AND VERY WET WEATHER IS EXPECTED THIS WEEKEND. THERE IS
POTENTIAL FOR AN ATMOSPHERIC RIVER AND ASSOCIATED HEAVY RAIN TO
DEVELOP OVER THE AREA...WITH SOME FLOODING POSSIBLE LATER THIS
WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...WEAK LOW PRESSURE CAN BE
SEEN ON NWS DOPPLER RADAR MOVING NORTHEASTWARD INTO SW WASHINGTON
THIS EVENING...WITH A VERY LOOSE CIRCULATION MOVING ACROSS THE
WILLAPA HILLS. THIS SYSTEM IS DECAYING...AND AS A RESULT THE AREAL
COVERAGE OF LIGHT RAIN AND CASCADE SNOW IS DECREASING THIS EVENING.
THAT SAID...THE AIR MASS REMAINS VERY MOIST AND FLOW REMAINS WEAKLY
CYCLONIC UP TO 700 MB. THEREFORE IT WOULD NOT BE SURPRISING TO SEE
AREAS OF -RA CONTINUE ACROSS OUR FORECAST AREA OVERNIGHT AND INTO
THURSDAY. ALSO...THE 00Z NAM/GFS KEY IN ON ANOTHER WEAK LOW OFF THE
SRN OREGON COAST WHICH IS BRINGING A BIT MORE LIGHT RAIN TO SW OREGON
THIS EVENING. THIS LOW IS EXPECTED TO LIFT N-NE AND DECAY WHILE
MOVING ACROSS OUR FORECAST AREA THURSDAY...BUT COULD HOLD TOGETHER
ENOUGH TO BRING SOME PERIODS OF LIGHT RAIN THROUGH THE DAY. KEEPING
THIS IN MIND...WE INCREASED POPS THROUGH THURSDAY...BUT QPF WILL BE
VERY LIGHT.

ATTENTION THEN TURNS TO THE NEXT MUCH STRONGER SYSTEM...PRESENTLY
PUSHING A COLD FRONT ACROSS 140W. THIS SYSTEM WILL BE A FAST
MOVER...LIKELY STARTING TO SPREAD MORE SIGNIFICANT RAIN ONSHORE BY
LATE THURSDAY AFTERNOON. 00Z NAM/GFS SUGGEST THE NORTH AND CENTRAL
OREGON COAST GET INTO THE WARM SECTOR AHEAD OF THE COLD FRONT...
OPENING THE DOOR FOR STRONGER WINDS TO SURFACE AT LEAST AT THE
BEACHES AND HEADLANDS THURSDAY AFTERNOON AND EVENING. GRADIENTS
APPEAR TO REMAIN EASTERLY ENOUGH TO KEEP THE STRONGEST WINDS OUT OF
THE COASTAL COMMUNITIES...BUT THE 00Z NAM AND 4KM UW WRFGFS HAVE BEEN
TRENDING STRONGER WITH THE COASTAL JET AHEAD OF THE FRONT. THE 00Z
NAM SHOWS 950 MB WINDS UP TO 60 KT WITHIN THE COASTAL JET. DECIDED
EARLIER IN THE SHIFT TO ISSUE A HIGH WIND WATCH FOR THE BEACHES AND
HEADLANDS BASED ON THE 00Z NAM DATA...AND WITH THE UW WRFGFS TRENDING
STRONGER WE FEEL EVEN MORE CONFIDENT ABOUT THAT DECISION. THIS WILL
MAINLY BE AN ISSUE FOR TRAVELERS ALONG EXPOSED AREAS OF COASTAL
ROUTES...WHILE MOST COASTAL COMMUNITIES WILL LIKELY JUST SEE A BRIEF
1-3 HR PERIOD OF 40-45 MPH GUSTS.

MADE VERY FEW CHANGES BEYOND THURSDAY NIGHT AS THE CURRENT FORECAST
LOOKS ON TRACK FOR A VERY WET AND OCCASIONALLY WINDY WEEKEND. 00Z NAM
AND GFS CERTAINLY HAVE NOT BACKED DOWN FROM THEIR EARLIER FORECASTS
FOCUSING AN ATMOSPHERIC RIVER SQUARELY ON SW WASHINGTON AND NW
OREGON...WITH FLOODING RAINS POSSIBLE. THE 00Z WRFGFS CONTINUES TO
PRODUCE VERY HEAVY QPF WITH UP TO 8-12 INCHES OF RAIN IN THE HIGHER
TERRAIN AND 2-4 INCHES IN THE WILLAMETTE VALLEY BY MONDAY...EVEN WITH
HEAVY RAIN SHADOWING. WILL NEED TO MONITOR THIS VERY CLOSELY OVER THE
NEXT FEW DAYS AS SIMILAR SITUATIONS HAVE PRODUCED FLOODING ON AREA
MAINSTEM RIVERS.  WEAGLE

.HYDROLOGY...WHILE RIVER FORECASTS OF CURRENT MODEL PRECIPITATION
INDICATE FLOODING IS POSSIBLE ON A RIVER OR TWO IN THE FORECAST AREA
SUNDAY INTO MONDAY...A LOOK AT THE MOST CORRELATED ANALOGS TO THE 96
HOUR GFS MODEL FORECAST SHED LIGHT ON FLOODING CHANCES ACROSS OUR
FORECAST AREA LATE IN THE WEEKEND AND EARLY NEXT WEEK. THE THREE
MOST CORRELATED ANALOG WEATHER PATTERNS TO THE CURRENT 96 HOUR GFS
MODEL FORECAST ARE LATE JANUARY 2003...EARLY JANUARY 1983 AND LATE
NOVEMBER 1999. ALL THREE OF THESE EVENTS PRODUCED ISOLATED TO
SCATTERED RIVER FLOODING WITHIN NORTHWEST OREGON AND/OR SOUTHWEST
WASHINGTON. WHILE THERE ARE CERTAINLY NOTABLE DIFFERENCES BETWEEN
THE CURRENT PATTERN AND EACH OF THESE HISTORICAL ANALOGS...SOME
CRITICAL WEATHER PARAMETERS APPEAR EVEN MORE FAVORABLE FOR PRODUCING
HEAVIER RAINS THAN THESE PAST EVENTS. THIS CERTAINLY HELPS BUILD
CONFIDENCE THERE WILL BE HYDROLOGICAL IMPACTS WITHIN OUR FORECAST
AREA OF RESPONSIBILITY SO LONG AS THE PATTERN HOLDS.
NONETHELESS...THERE IS STILL CONSIDERABLE UNCERTAINTY IN WHERE THE
HEAVIEST RAIN WILL SET UP...AND EXACTLY WHICH RIVERS WILL FLOOD AND
WHEN. PLEASE CONTINUE TO MONITOR THE FORECAST IF YOU LIVE NEAR ANY
RIVERS FED BY THE THE CASCADES OR COAST RANGE...AND PLEASE SEE
WATER.WEATHER.GOV/AHPS2/INDEX.PHP?WFO=PQR FOR THE LATEST RIVER
FORECASTS. /NEUMAN

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...A MOIST LOWER ATMOSPHERE...DECREASING WINDS AND
VARYING VFR CLOUD DECKS SCATTERED OVER THE FORECAST WILL RESULT IN
A MIX OF IFR TO VFR CONDITIONS ACROSS THE AREA OVERNIGHT. SUSPECT
SOME DETERIORATION AT MOST TAF SITES. AS THE NEXT COLD FRONT
APPROACHES THE AREA THURSDAY...EXPECT SOUTHEAST TO EAST WINDS TO
INCREASE AGAIN...AND CAUSE MOST SITES WITH FLIGHT RESTRICTIONS TO
TURN VFR. EXPECT A PERIOD OF HIGH END IFR TO MVFR AS THE COLD
FRONT PUSHES INTO THE COAST AROUND 03Z FRIDAY...AND LIKELY AFTER
06Z FRIDAY FOR INTERIOR TAF SITES.

KPDX AND APPROACHES...DUE TO AMPLE LOW LEVEL MOISTURE AND
DECREASING WINDS OVER THE NEXT FEW HOURS...SUSPECT SOME
DETERIORATION...BUT CONFIDENCE IN THE DETAILS IS LOW.
HOWEVER...INCREASING EAST WINDS THURSDAY MORNING SHOULD ALLOW
ANY FLIGHT RESTRICTIONS TO DISAPPEAR. THEREAFTER...EXPECT
PRIMARILY VFR CONDITIONS THROUGH 06Z FRIDAY AS EAST WINDS CONTINUE
AHEAD OF A MODEST COLD FRONT. /NEUMAN

&&

.MARINE...SEAS CONTINUE TO HOVER NEAR 10 FT SO A SMALL CRAFT FOR
HAZARDOUS SEAS WAS EXTENDED THROUGH 4 AM...ALTHOUGH SEAS SHOULD
DROP SOLIDLY BELOW THIS HEIGHT WELL BEFORE THIS TIME. A MORE
ORGANIZED FRONTAL STORM SYSTEM WILL CAUSE IN WINDS TO INCREASE
ACROSS THE WATERS ON THURSDAY...PARTICULARLY OVER THE OUTER
WATERS. EVENTUALLY...THE FRONT WILL PUSH INTO THE WATERS DURING
THE EVENING AND PRODUCE A 3 TO 6 HOUR PERIOD OF GALE FORCE WIND
GUSTS OF 40 TO 45 KT ACROSS THE WATERS. SEAS SHOULD RESPOND
ACCORDINGLY AND RISE INTO AT LEAST THE MID TEENS. EXPECT SEAS TO
SUBSIDE FAIRLY QUICKLY BACK DOWN INTO THE 10 TO 12 FT RANGE LATE
THURSDAY NIGHT INTO EARLY FRIDAY MORNING. HOWEVER...THESE LOWER
WAVE HEIGHTS WILL BE SHORT LIVED AS AN IMPRESSIVE LONG PERIOD
WESTERLY SWELL WILL LIKELY ARRIVE FRIDAY AFTERNOON INTO FRIDAY
EVENING. WAVE HEIGHTS MAY NEARLY DOUBLE IN A 6 HOUR PERIOD SO THIS
COULD CERTAINLY CATCH OFF GUARD ANY UNINFORMED MARINERS THAT
VENTURE OUT FRIDAY MORNING. CONFIDENCE IS RELATIVELY HIGH THAT THIS
SWELL WILL LIKELY EXCEED 20 FT. IN FACT...THESE PATTERNS OFTEN
PRODUCE HIGHER SEAS THAN FORECASTED BY THE ENP WAVE MODEL. A HIGH
SURF ADVISORY APPEARS LIKELY. THE GOOD NEWS IS THAT THE LARGEST
SWELL WILL LIKELY ARRIVE DURING LOW TIDE AND DURING THE NIGHT TIME
HOURS WHEN MOST MARINERS AND BEACH GOERS ARE NOT IN HARMS WAY.

THIS SWELL TRAIN WILL SUBSIDE SATURDAY...BUT ANOTHER STRONG
FRONTAL STORM SYSTEM WILL LIKELY PRODUCE GALE FORCE TO POSSIBLY
LOW END STORM FORCE GUSTS ACROSS THE WATERS ON SATURDAY. THIS WILL
EFFECTIVELY KEEP SEAS FLIRTING WITH THE 20 FT MARK ON SATURDAY.

NORMAL HIGH TIDE AT TOKE POINT WASHINGTON IS SUPPOSED TO BE 10.3
FT SATURDAY AROUND 11 AM. WITH SOUTHERLY WINDS SUPPORTING A
POSITIVE TIDAL ANOMALY OF AROUND 0.5 FT...HIGH TIDE WILL APPROACH
11 FT AND MAY RESULT IN SOME MINOR TIDAL OVERFLOW FLOODING IN
WILLAPA BAY. GIVEN THE HEAVIER RAINS WILL NOT HAVE ARRIVED...THE
WILLAPA RIVER IS FORECASTED TO BE AROUND 20 PERCENT OF FLOOD
FLOW ON SATURDAY...WHICH SHOULD HELP MITIGATE MORE WIDESPREAD
COASTAL FLOODING CONCERNS.

HIGH PRESSURE WILL SLOWLY BUILD OVER THE NORTHEAST PACIFIC LATE IN
THE WEEKEND AND INTO EARLY NEXT WEEK...WHICH SHOULD RESULT IN
WINDS AND SEAS RELAXING QUITE A BIT WHEN COMPARED TO THE
FRIDAY/SATURDAY TIME FRAME. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
     EVENING FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 AM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM
     PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.



000
FXUS66 KSEW 180506
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST WED DEC 17 2014

.SYNOPSIS...A WEAK UPPER TROUGH WILL MOVE EAST OF THE CASCADES LATE
TONIGHT. THE NEXT FRONTAL SYSTEM WILL BRING RAINY AND LOCALLY WINDY
WEATHER TO WESTERN WASHINGTON LATER THURSDAY AND THURSDAY NIGHT...
WITH SHOWERS DECREASING FRIDAY. WINDY RAINY WEATHER WILL CONTINUE
THIS WEEKEND AS A VIGOROUS FRONTAL SYSTEM MOVES THROUGH THE PACIFIC
NORTHWEST. SOMEWHAT DRIER WEATHER IS LIKELY EARLY NEXT WEEK.

&&

.SHORT TERM...A WEAK UPPER TROUGH IS MOVING ACROSS WESTERN
WASHINGTON THIS EVENING. AREAS OF LIGHT RAIN CONTINUE ACROSS THE
AREA...ESPECIALLY IN THE PUGET SOUND REGION. THE UPPER TROUGH WILL
MOVE EAST OF THE CASCADES LATE TONIGHT...AND A SMALL UPPER RIDGE
WILL MOVE INTO THE OFFSHORE WATERS. THEN THE RIDGE WILL PROGRESS
INLAND QUICKLY ON THURSDAY...MOVING INTO EASTERN WASHINGTON BY LATE
AFTERNOON.

A PACIFIC FRONTAL SYSTEM WILL START SPREADING RAIN INTO WESTERN
WASHINGTON THURSDAY...PROBABLY JUST BEHIND THE UPPER RIDGE
AXIS...WITH PRECIPITATION CONTINUING THURSDAY NIGHT AS THE SYSTEM
MOVES INLAND. THE UPPER TROUGH FOLLOWING THE COLD FRONT WILL MOVE
THROUGH WESTERN WASHINGTON ON FRIDAY. THIS IS NOT AN ESPECIALLY
STRONG FRONT FOR DECEMBER...BUT IT WILL BRING STEADY RAIN AND
LOCALLY WINDY CONDITIONS TO THE COAST AND NORTH INTERIOR.

STORM TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD ENDING FRIDAY
AFTERNOON SHOULD BE 0.75 TO 1.5 INCHES OVER MOST OF THE MOUNTAINS...
WITH UP TO 1 INCH AT THE COAST...AND 0.25 TO 0.75 OVER MOST OF THE
INTERIOR LOWLANDS. THEN SNOW LEVEL WILL RISE TO 4000 TO 5000 FT
THURSDAY NIGHT...THEN FALL TO AROUND 3500 FT FRIDAY. STORM TOTAL
SNOWFALL AT THE HIGHER PASSES AND SKI RESORTS SHOULD AMOUNT TO 3 TO
8 INCHES OR SO.

A VIGOROUS FRONTAL SYSTEM WILL MOVE QUICKLY INTO WESTERN WASHINGTON
LATE FRIDAY NIGHT AND SATURDAY. IT WILL BRING ANOTHER ROUND OF
LOCALLY WINDY CONDITIONS...STEADY RAIN TO THE WESTERN WASHINGTON
LOWLANDS...AND RAIN AND SNOW TO THE MOUNTAINS WITH SOMEWHAT HIGHER
SNOW LEVELS.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
FORECAST DISCUSSION -- MODELS NOW SHOW A BREAK OR AT LEAST DECREASE
IN RAINFALL RATES SUNDAY NIGHT AS WEAK HIGH PRESSURE TEMPORARILY
BUILDS OFFSHORE. THE RIDGE WILL LIFT THE FLOW NWD SO MOISTURE
DIRECTED INTO SRN WA/OREGON WILL LIFT BACK OVER WRN WA ON MONDAY.
THE RIDGING IS QUITE A BIT STRONGER ON MOST OF TODAY`S MODEL RUNS
WHICH WOULD SHUT OFF PRECIPITATION BY LATE MONDAY OR MONDAY NIGHT.
THE GOOD NEWS IS THAT IF HEAVY RAIN DOES DEVELOP IT APPEARS THERE
WILL BE SOME SHIFTING BETWEEN THE CASCADES OF WRN WA/WRN OREGON.
THIS SHOULD LIMIT POTENTIAL QPF IN ANY ONE PARTICULAR AREA. MODELS
NOW SHOW 24 TO 36 HOUR QPF AMOUNTS OF 4 TO 6 INCHES MORE EVENLY
DISTRIBUTED ALONG THE WA/OREGON CASCADES. THIS IS STILL ENOUGH FOR
SOME MINOR FLOODING ON THE MORE PRONE RIVERS SO FORECASTS SHOULD BE
MONITORED CLOSELY.

ANOTHER SURFACE LOW WILL TRACK INTO WRN WA OR NRN OREGON AROUND
TUESDAY. MODELS NO LONGER TAP THIS LOW FOR A CONTINUOUS MOISTURE
STREAM WHICH INSTEAD ARRIVES AFTER A BREAK IN RAINFALL. MODELS ARE
ALSO TRENDING MUCH WEAKER WITH THIS LOW SO ADDITIONAL RAIN AMOUNTS
LOOK TO BE LIGHT AND NOT HYDROLOGICALLY SIGNIFICANT.

LONG RANGE MODELS ARE INDICATING A POSSIBLE PATTERN CHANGE BY THE
MIDDLE OF NEXT WEEK. HOWEVER...MODELS DIFFER ON THE POSITIONING OF A
HIGH OVER KONA LOW PATTERN OVER THE PACIFIC WHICH WILL DETERMINE THE
STRENGTH OF NLY FLOW OVER WRN WA. THE 12/18Z GFS IS FURTHER E WITH
THE LOW AND DUMPS MOST THE COLD AIR INTO THE ROCKIES. COLDER AIR
WOULD ARRIVE ACROSS WRN WA IF THE ECMWF SOLUTION VERIFIED WITH THE
LOW FURTHER W. EITHER WAY...A TRANSITION TO COOLER TEMPERATURES IS
LIKELY ENOUGH TO TREND HIGH/LOW TEMPS DOWNWARD A BIT FOR WEDNESDAY.
MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY NIGHT AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. THE
LATEST 12Z GFS/ECMWF ARE FASTER WITH THE TRAILING FRONTAL BAND AND
PUSHES IT SWD INTO OREGON BY MONDAY. THIS COULD HELP MITIGATE ANY
RIVER FLOODING THAT DEVELOPS BUT DOES NOT END THE THREAT AS MODELS
HAVE NOT ALL SETTLED ON A PARTICULAR SOLUTION. 24 TO 36 HOUR RAIN
AMOUNTS ARE STILL AVERAGING ABOUT 4 TO 5 INCHES OVER THE WA CASCADES
WHICH COULD CAUSE FLOODING ON PRONE RIVERS. AT THIS TIME...PRIMARY
CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE SKOKOMISH BUT
ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE STREAMS. MERCER

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH IS OVER WESTERN WASHINGTON
THIS EVENING WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS IS MOIST
AND STABLE WITH WEAK SURFACE GRADIENTS. A COLD FRONT ABOUT 650 NM
WEST OF SEATTLE AT 04Z WILL PUSH INTO THE REGION THURSDAY EVENING
WITH STRONG SOUTHWEST FLOW ALOFT.

AREAS OF LIGHT RAIN WILL PERSIST ACROSS WESTERN WASHINGTON OVERNIGHT
WITH WIDESPREAD MVFR CEILINGS AND LOCALIZED IFR. SOME TEMPORARY
IMPROVEMENT TO VFR IS POSSIBLE MIDDAY THURSDAY AS A TRANSITORY UPPER
RIDGE MOVES OVER THE AREA AND SURFACE GRADIENTS BECOME INCREASINGLY
OFFSHORE. WIDESPREAD RAIN WILL SPREAD BACK INTO THE AREA BY EARLY
EVENING AHEAD OF THE NEXT FRONT WITH CEILINGS FALLING BACK TO MVFR.

KSEA...MVFR THROUGH THE NIGHT WITH LIGHT RAIN AT TIMES. VFR CEILINGS
AT OR ABOVE 5K FEET POSSIBLE 18Z-00Z BUT WILL DROP AGAIN WITH MORE
RAIN THURSDAY EVENING. LIGHT SOUTH-SOUTHEAST WIND
OVERNIGHT...BECOMING SOUTHEAST 7 TO 12 KNOTS THURSDAY AFTERNOON.

&&

.MARINE...A WEAK TROUGH LIES OVER THE WATERS THIS EVENING FOR LIGHT
WINDS. A STRONG FRONT ASSOCIATED WITH A 970-975 MB LOW WEST OF
HAIDA GWAII WILL MOVE THROUGH THE OFFSHORE WATERS ON THURSDAY...THEN
INLAND THURSDAY NIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED
OVER THE COASTAL WATERS THURSDAY AFTERNOON THROUGH THURSDAY NIGHT
WITH SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT
ENTRANCES...NORTHERN INLAND WATERS...AND ADMIRALTY INLET. LONG
PERIOD SWELL NEAR 22 FEET ARE STILL EXPECTED ON THE COAST LATE
FRIDAY AFTERNOON AND FRIDAY NIGHT. TIDAL ANOMALIES ALONG THE COAST
ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH TIDE OCCURS SATURDAY
MORNING. IF SWELL REMAINS HIGH INTO SATURDAY MORNING
AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS POSSIBLE. ANOTHER
STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE FORCE WINDS ONCE
AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN INLAND
WATERS...AND THE STRAIT ENTRANCES. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






000
FXUS66 KSEW 180506
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST WED DEC 17 2014

.SYNOPSIS...A WEAK UPPER TROUGH WILL MOVE EAST OF THE CASCADES LATE
TONIGHT. THE NEXT FRONTAL SYSTEM WILL BRING RAINY AND LOCALLY WINDY
WEATHER TO WESTERN WASHINGTON LATER THURSDAY AND THURSDAY NIGHT...
WITH SHOWERS DECREASING FRIDAY. WINDY RAINY WEATHER WILL CONTINUE
THIS WEEKEND AS A VIGOROUS FRONTAL SYSTEM MOVES THROUGH THE PACIFIC
NORTHWEST. SOMEWHAT DRIER WEATHER IS LIKELY EARLY NEXT WEEK.

&&

.SHORT TERM...A WEAK UPPER TROUGH IS MOVING ACROSS WESTERN
WASHINGTON THIS EVENING. AREAS OF LIGHT RAIN CONTINUE ACROSS THE
AREA...ESPECIALLY IN THE PUGET SOUND REGION. THE UPPER TROUGH WILL
MOVE EAST OF THE CASCADES LATE TONIGHT...AND A SMALL UPPER RIDGE
WILL MOVE INTO THE OFFSHORE WATERS. THEN THE RIDGE WILL PROGRESS
INLAND QUICKLY ON THURSDAY...MOVING INTO EASTERN WASHINGTON BY LATE
AFTERNOON.

A PACIFIC FRONTAL SYSTEM WILL START SPREADING RAIN INTO WESTERN
WASHINGTON THURSDAY...PROBABLY JUST BEHIND THE UPPER RIDGE
AXIS...WITH PRECIPITATION CONTINUING THURSDAY NIGHT AS THE SYSTEM
MOVES INLAND. THE UPPER TROUGH FOLLOWING THE COLD FRONT WILL MOVE
THROUGH WESTERN WASHINGTON ON FRIDAY. THIS IS NOT AN ESPECIALLY
STRONG FRONT FOR DECEMBER...BUT IT WILL BRING STEADY RAIN AND
LOCALLY WINDY CONDITIONS TO THE COAST AND NORTH INTERIOR.

STORM TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD ENDING FRIDAY
AFTERNOON SHOULD BE 0.75 TO 1.5 INCHES OVER MOST OF THE MOUNTAINS...
WITH UP TO 1 INCH AT THE COAST...AND 0.25 TO 0.75 OVER MOST OF THE
INTERIOR LOWLANDS. THEN SNOW LEVEL WILL RISE TO 4000 TO 5000 FT
THURSDAY NIGHT...THEN FALL TO AROUND 3500 FT FRIDAY. STORM TOTAL
SNOWFALL AT THE HIGHER PASSES AND SKI RESORTS SHOULD AMOUNT TO 3 TO
8 INCHES OR SO.

A VIGOROUS FRONTAL SYSTEM WILL MOVE QUICKLY INTO WESTERN WASHINGTON
LATE FRIDAY NIGHT AND SATURDAY. IT WILL BRING ANOTHER ROUND OF
LOCALLY WINDY CONDITIONS...STEADY RAIN TO THE WESTERN WASHINGTON
LOWLANDS...AND RAIN AND SNOW TO THE MOUNTAINS WITH SOMEWHAT HIGHER
SNOW LEVELS.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
FORECAST DISCUSSION -- MODELS NOW SHOW A BREAK OR AT LEAST DECREASE
IN RAINFALL RATES SUNDAY NIGHT AS WEAK HIGH PRESSURE TEMPORARILY
BUILDS OFFSHORE. THE RIDGE WILL LIFT THE FLOW NWD SO MOISTURE
DIRECTED INTO SRN WA/OREGON WILL LIFT BACK OVER WRN WA ON MONDAY.
THE RIDGING IS QUITE A BIT STRONGER ON MOST OF TODAY`S MODEL RUNS
WHICH WOULD SHUT OFF PRECIPITATION BY LATE MONDAY OR MONDAY NIGHT.
THE GOOD NEWS IS THAT IF HEAVY RAIN DOES DEVELOP IT APPEARS THERE
WILL BE SOME SHIFTING BETWEEN THE CASCADES OF WRN WA/WRN OREGON.
THIS SHOULD LIMIT POTENTIAL QPF IN ANY ONE PARTICULAR AREA. MODELS
NOW SHOW 24 TO 36 HOUR QPF AMOUNTS OF 4 TO 6 INCHES MORE EVENLY
DISTRIBUTED ALONG THE WA/OREGON CASCADES. THIS IS STILL ENOUGH FOR
SOME MINOR FLOODING ON THE MORE PRONE RIVERS SO FORECASTS SHOULD BE
MONITORED CLOSELY.

ANOTHER SURFACE LOW WILL TRACK INTO WRN WA OR NRN OREGON AROUND
TUESDAY. MODELS NO LONGER TAP THIS LOW FOR A CONTINUOUS MOISTURE
STREAM WHICH INSTEAD ARRIVES AFTER A BREAK IN RAINFALL. MODELS ARE
ALSO TRENDING MUCH WEAKER WITH THIS LOW SO ADDITIONAL RAIN AMOUNTS
LOOK TO BE LIGHT AND NOT HYDROLOGICALLY SIGNIFICANT.

LONG RANGE MODELS ARE INDICATING A POSSIBLE PATTERN CHANGE BY THE
MIDDLE OF NEXT WEEK. HOWEVER...MODELS DIFFER ON THE POSITIONING OF A
HIGH OVER KONA LOW PATTERN OVER THE PACIFIC WHICH WILL DETERMINE THE
STRENGTH OF NLY FLOW OVER WRN WA. THE 12/18Z GFS IS FURTHER E WITH
THE LOW AND DUMPS MOST THE COLD AIR INTO THE ROCKIES. COLDER AIR
WOULD ARRIVE ACROSS WRN WA IF THE ECMWF SOLUTION VERIFIED WITH THE
LOW FURTHER W. EITHER WAY...A TRANSITION TO COOLER TEMPERATURES IS
LIKELY ENOUGH TO TREND HIGH/LOW TEMPS DOWNWARD A BIT FOR WEDNESDAY.
MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY NIGHT AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. THE
LATEST 12Z GFS/ECMWF ARE FASTER WITH THE TRAILING FRONTAL BAND AND
PUSHES IT SWD INTO OREGON BY MONDAY. THIS COULD HELP MITIGATE ANY
RIVER FLOODING THAT DEVELOPS BUT DOES NOT END THE THREAT AS MODELS
HAVE NOT ALL SETTLED ON A PARTICULAR SOLUTION. 24 TO 36 HOUR RAIN
AMOUNTS ARE STILL AVERAGING ABOUT 4 TO 5 INCHES OVER THE WA CASCADES
WHICH COULD CAUSE FLOODING ON PRONE RIVERS. AT THIS TIME...PRIMARY
CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE SKOKOMISH BUT
ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE STREAMS. MERCER

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH IS OVER WESTERN WASHINGTON
THIS EVENING WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS IS MOIST
AND STABLE WITH WEAK SURFACE GRADIENTS. A COLD FRONT ABOUT 650 NM
WEST OF SEATTLE AT 04Z WILL PUSH INTO THE REGION THURSDAY EVENING
WITH STRONG SOUTHWEST FLOW ALOFT.

AREAS OF LIGHT RAIN WILL PERSIST ACROSS WESTERN WASHINGTON OVERNIGHT
WITH WIDESPREAD MVFR CEILINGS AND LOCALIZED IFR. SOME TEMPORARY
IMPROVEMENT TO VFR IS POSSIBLE MIDDAY THURSDAY AS A TRANSITORY UPPER
RIDGE MOVES OVER THE AREA AND SURFACE GRADIENTS BECOME INCREASINGLY
OFFSHORE. WIDESPREAD RAIN WILL SPREAD BACK INTO THE AREA BY EARLY
EVENING AHEAD OF THE NEXT FRONT WITH CEILINGS FALLING BACK TO MVFR.

KSEA...MVFR THROUGH THE NIGHT WITH LIGHT RAIN AT TIMES. VFR CEILINGS
AT OR ABOVE 5K FEET POSSIBLE 18Z-00Z BUT WILL DROP AGAIN WITH MORE
RAIN THURSDAY EVENING. LIGHT SOUTH-SOUTHEAST WIND
OVERNIGHT...BECOMING SOUTHEAST 7 TO 12 KNOTS THURSDAY AFTERNOON.

&&

.MARINE...A WEAK TROUGH LIES OVER THE WATERS THIS EVENING FOR LIGHT
WINDS. A STRONG FRONT ASSOCIATED WITH A 970-975 MB LOW WEST OF
HAIDA GWAII WILL MOVE THROUGH THE OFFSHORE WATERS ON THURSDAY...THEN
INLAND THURSDAY NIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED
OVER THE COASTAL WATERS THURSDAY AFTERNOON THROUGH THURSDAY NIGHT
WITH SMALL CRAFT ADVISORY CONDITIONS FOR THE STRAIT
ENTRANCES...NORTHERN INLAND WATERS...AND ADMIRALTY INLET. LONG
PERIOD SWELL NEAR 22 FEET ARE STILL EXPECTED ON THE COAST LATE
FRIDAY AFTERNOON AND FRIDAY NIGHT. TIDAL ANOMALIES ALONG THE COAST
ARE JUST OVER 1 FOOT ABOVE NORMAL AND HIGH TIDE OCCURS SATURDAY
MORNING. IF SWELL REMAINS HIGH INTO SATURDAY MORNING
AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS POSSIBLE. ANOTHER
STRONG FRONT WILL ARRIVE ON SATURDAY WITH GALE FORCE WINDS ONCE
AGAIN LIKELY OVER THE COASTAL WATERS...THE NORTHERN INLAND
WATERS...AND THE STRAIT ENTRANCES. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KOTX 172356
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
356 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
00Z TAFS: A weak weather disturbance is generating light precip
across eastern WA and in the ID Panhandle late this afternoon.
This wave will begin to exit over the course of this evening, but
will be followed by another overnight with more light precip to
fill in across the region. Low level winds will also veer through
tonight, which will result in more favorable upslope flow for
stratus formation. Expect cigs/vis to deteriorate tonight at
KGEG, KSFF, KCOE and KPUW with IFR/MVFR conditions and localized
LIFR conditions possible. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 172356
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
356 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
00Z TAFS: A weak weather disturbance is generating light precip
across eastern WA and in the ID Panhandle late this afternoon.
This wave will begin to exit over the course of this evening, but
will be followed by another overnight with more light precip to
fill in across the region. Low level winds will also veer through
tonight, which will result in more favorable upslope flow for
stratus formation. Expect cigs/vis to deteriorate tonight at
KGEG, KSFF, KCOE and KPUW with IFR/MVFR conditions and localized
LIFR conditions possible. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 172252
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
252 PM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will continue through the end of the
week with periods of light snow in the mountains...and rain or
snow in the valleys. Lower elevations from Interstate 90 south
will see mainly rain...while areas in the Cascades and near the
Canadian border will remain mainly snow. A much stronger weather
system over the weekend will usher in warmer temperatures with
sharply rising snow levels...as well as the potential for windy
conditions.

&&

.DISCUSSION...

Tonight and Tomorrow...A number of small weak disturbances running
across Eastern Washington and Northern Idaho through tonight and
tomorrow. They are very difficult to pick out in some of the
models as there is too much clutter in the flow associated with
the weakening baroclinic band upon where these disturbances are
located near that is currently passing through the area. They
haven`t been showing up too well in the radar either as they have
been far enough away for most of the day for the base elevation
beam to get a return on as well. Best bet to find these features
has been the IR satellite imagery on a fast rock and picking out
the small scale rotation and cloud top cooling. One such feature
is moving northeast this afternoon and is causing precipitation
just east of Moses Lake up to Omak and some points to the north
and east. A second feature, appearing to almost be a southern part
of the splitting/weakening baroclinic band has brought light rain
to Lewiston. All of these disturbances translate to the Northeast
and East at varying times tonight and tomorrow and as such the
pops and QPF show a general favoring of locations to the North and
East (including locations near Spokane down to Pullman) to receive
some precipitation but as expected the amounts are not too
significant...still it doesn`t take too much liquid to pool on
pavement that in turn cools overnight to allow for slick
conditions in spots similar to what occurred this morning.
/Pelatti

Thursday night through Sunday...An active weather pattern is
expected especially over the weekend with two systems to impacts
the Inland Northwest during this forecast period.

Thursday night/Friday: A large upper low seen on Infrared
Satellite Imagery in the Gulf of Alaska will drop southeast
sending a cold front across the area. The timing of the front
tracks into Central Washington Thursday night during the overnight
hours...reaching Eastern Washington and North Idaho Friday
morning. A north-south oriented jet parallel to the front and
southerly low/mid level flow will minimize downslope flow with all
areas likely to receive some precipitation. Inspection of model
soundings suggest this to be a mainly valley rain or rain/snow
mix...with snow in the mountains. 850mb winds backing to the south
will aid in bring up warmer air from the south. However a wedge of
cooler air trapped along the East Slopes of the Cascades will
result in lower snow levels over North Central Washington with the
potential for 2-3 inches of snow accumulation above 1000-1500
feet. This includes the Methow Valley, Plain, Waterville Plateau,
higher portions of Omak, and Republic. The Wenatchee area and
lower portions of the Okanogan and Columbia River valleys are
expected to see mainly a rain/snow mix or wet non-accumulating
snow. The mountains will generally see 2-5 inches of snow with the
Cascades seeing the highest amounts.

Saturday through Sunday...A much stronger system is expected this
weekend bringing a wide variety of expected weather. The models
continue to show an atmospheric river as a subtropical moisture
fetch becomes aimed at the area. The leading edge of this moisture
will enter on Saturday in the form of a warm front. Strong
isentropic lift will result in the development of widespread
rain and snow. 850mb winds backing to the south-southeast will
favor upslope flow into the northern mountains, with cooler air
remaining banked up into the Cascades, Okanogan Valley, and
Okanogan Highlands. Models suggest the potential for moderate to
locally heavy snow accumulations in these areas along and ahead of
the warm front before snow levels rise from south to north
Saturday night into Sunday morning. Snow levels will be fast to
rise from Interstate 90 south with precip expected to fall as
mainly valley rain and mountain snow. The valleys north of Spokane
such as Colville, Metaline Falls, Priest Lake, and Bonners Ferry
may start off as snow on Saturday with light accumulations...before
changing to rain Saturday night. As the warmer air aloft pokes
into the Cascades Saturday night...the valleys will likely have a
hard time mixing out with freezing rain possible especially south
of Lake Chelan in places like Plain and Leavenworth.

On Sunday the atmospheric river shifts south near the
Washington/Oregon border with strong westerly flow over the area.
This will lead to a strong rain shadow east of the Cascades with
precipitation likely confined mainly to the Cascade crest, Idaho
Panhandle, and southeast Washington. 850mb winds of 25-35 kts and
possible sun breaks across the Columbia Basin...and 850mb temps of
3-6C could lead to very mild temperatures along with breezy to
windy conditions. For now went a bit above MOS guidance which
usually does not go warm enough in these situations. JW

Sunday Nt through Christmas Eve: Following the passage of the windy
and wet short-wave trough that will move through broad upper
ridging Sunday Nt, what`s left of a stalled cold frontal boundary
will remain over Nrn Oregon and extreme Srn Wa Tues and keep the
threat of pcpn in the fcst for the Lewiston area as well as the Camas
Prairie. Where this front stalls will be critical as far as the
Christmas Eve fcst, because it is this boundary that will combine
with a significant short-wave trough and vort max moving into the
region as it translates SE down the BC coast. Deep cyclogenesis is
fcst by most model guidance over Ern Oregon Wednesday as the flow
backs and increases lift over the aforementioned boundary. As
pressure gradients increase, cold air will then begin to move into
Ern Wa from Srn Bc. Though it`s unusual even to see modest amnts
of agreement among models as to the placement of this deep low 7
days out, there still are enough differences how far south the
low will track that still make our level of confidence low as to where
potentially heavy snow bands may set up Christmas Eve. The trend,
however, has been slightly south which would keep the higher snow
threat out of Nrn Wa. Stay tuned... bz

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  37  33  39  31  40 /  50  30  40  90  10  70
Coeur d`Alene  33  38  32  39  32  39 /  60  60  20 100  20  70
Pullman        33  43  34  42  32  43 /  50  40  40  90  10  70
Lewiston       35  45  36  46  33  47 /  40  30  20  70  10  40
Colville       32  37  34  38  32  38 /  60  30  60 100  10  80
Sandpoint      32  37  32  36  31  38 /  60  60  30 100  40  60
Kellogg        32  38  32  36  31  36 /  70  70  20 100  40  60
Moses Lake     29  39  36  42  30  39 /  20  10  70  70  10  70
Wenatchee      31  37  33  40  30  34 /  30  10  70  60  10  70
Omak           27  34  32  37  30  33 /  40  10  80  80  10  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 172252
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PST WED DEC 17 2014

.SYNOPSIS...WEAK LOW PRESSURE WILL CROSS THE AREA THIS EVENING WITH
SHOWERS LINGERING OVERNIGHT. EXPECT FAIRLY QUIET WEATHER TO START
THE DAY THURSDAY. A MORE ORGANIZED FRONT WILL BRING GUSTY WINDS TO
THE COAST WITH RAIN SPREADING INLAND THURSDAY NIGHT AND FRIDAY.
RISING SNOW LEVELS WILL LIMIT SNOW TO THE HIGHEST PEAKS. COLDER AIR
BEHIND THE FRONT WILL BRING ACCUMULATING SNOW SHOWERS FOR THE
CASCADES PASSES FRIDAY EVENING AND SATURDAY. MILD AND VERY WET
WEATHER ARRIVED THIS WEEKEND. THERE IS POTENTIAL FOR AN ATMOSPHERIC
RIVER AND ASSOCIATED HEAVY RAIN TO DEVELOP OVER THE AREA AFFECTING
RIVERS INTO NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH SATURDAY...A WEAK AND SPLITTING TROUGH
WILL SEND MOST OF ITS ENERGY SOUTH OF OUR AREA TONIGHT. WILL SEE
SHOWERS TAPER OFF OVERNIGHT AS HIGH PRESSURE BEGINS A TRANSIT ACROSS
THE AREA. WILL ALSO SEE CORRESPONDING SNOW LEVELS RISE ABOVE THE
PASSES AND GENERALLY LIMIT THE AMOUNT OF ACCUMULATIONS. THE RIDGE
AXIS QUICKLY PASSES EAST BY TOMORROW AFTERNOON LEADING TO A LARGELY
DRY DAY FOR THE INTERIOR.

ANOTHER MORE COHESIVE TROUGH AND FRONTAL SYSTEM WILL DIG OFFSHORE
WITH WARM FRONTAL RAIN TOUCHING THE COAST LATE FRIDAY AFTERNOON WITH
HEAVIER AMOUNTS BY EARLY FRIDAY EVENING. TIMING COULD BE EARLIER
DEPENDING ON MODEL OF CHOICE WITH THE GFS PERHAPS A COUPLE HOURS
FASTER THAN THE ECMWF AND THE NAM SLOWER YET. NAM TYPICALLY DOES NOT
HANDLE WARM PROCESS RAIN VERY WELL SO AM PUTTING LESS WEIGHT ON IT
TO START WITH. AS THE RAIN COMES IN...A COASTAL JET DEVELOPS
BRINGING FAIRLY GUSTY WINDS TO THE COAST AND COAST RANGE BUT NOTHING
TOO OUT OF THE ORDINARY. NOT ANTICIPATING ANY HIGHLIGHTS BUT
PROBABLY A RUN OF THE MILL WINDY COASTAL STORM. THE ASSOCIATED COLD
FRONT COME ASHORE AROUND 12Z FRIDAY MORNING AND CROSSES THE CASCADES
AROUND 17Z WITH COLDER AIR AND LOWERING SNOW LEVELS WITH AND MORE SO
BEHIND IT. PRECIPITATION TAPERS OFF AND BECOMES MORE SHOWERY IN
NATURE BEHIND THE FRONT. EXPECT LIGHT ACCUMULATING SNOW BEGINS AT
WILLAMETTE PASS AROUND DAY BREAK AND LOWERS TO NEAR GOVERNMENT PASS
LATER THAT MORNING. THE SNOW COMES TO BE TOO LITTLE...TOO LATE FOR
MUCH APPRECIABLE INCREASE IN THE SNOW PACK WITH PERHAPS A FEW INCHES
AT THE HIGHER PASSES AND LESS THAN AN INCH FOR GOVERNMENT CAMP.
HIGHER PEAKS COULD SEE UP TO A FOOT...HOWEVER. ANY OF THE MID
ELEVATION SNOW WILL BE RATHER SHORT-LIVED AS SNOW LEVELS IMMEDIATELY
BEGIN RISING IN ANTICIPATION OF THE PACIFIC STORM TRACK BECOMING
CENTERED OVER THE AREA.

MAIN ATTENTION THIS SHIFT HAS BEEN BE PLACED ON THE ATMOSPHERIC
RIVER EVENT SETTING UP TO AFFECT THE REGION THIS WEEKEND WITH
IMPACTS LASTING INTO NEXT WEEK. RAW GFS MODEL RUN ACCUMULATED QPF
AMOUNTS EXCEED 12 INCHES FOR PORTIONS OF THE CASCADES AND 10 INCHES
FOR THE COAST RANGE ENDING MONDAY MORNING. WILL SEE THE WARM RAINS
BEGIN AFFECTING THE COAST RANGE SATURDAY MORNING AND PUSH QUICKLY
INLAND TO THE CASCADES BY SATURDAY AFTERNOON. MOST OF THE HEAVY RAIN
OCCURS BEGINNING SATURDAY NIGHT. THERE WOULD BE DEEP WESTERLY FLOW
FROM THE SURFACE UP TO THE JET LEVEL THUS EXPECT THIS COULD BE AN
IDEAL OROGRAPHIC SITUATION TO EXTRACT A MAXIMUM AMOUNT OF RAIN FROM
WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE SUPPORT FROM THE
ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS FOLLOWING THE
HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT REALITY BRINGS
SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL RUNS STAY
UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM RIVERS
EXCEEDING FLOOD STAGE AS SOON AS SUNDAY EVENING.

HAVE ISSUED SOME OUTLOOK PRODUCTS TODAY LOOKING AHEAD TO FLOODING
POTENTIAL WITH THE CAVEAT THAT MODELS HAVE SHIFTED THE FOCUS FROM
NORTHERN WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA DURING THE
PAST 36 HOURS. ADDITIONAL SHIFTING IS EXPECTED AS WELL AS TIMING
DIFFERENCES. STAY TUNED AS THIS SITUATION EVOLVES OVER TIME.
/JBONK

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MODELS MAINTAIN A
FLATTENED RIDGE OVER THE EASTERN PACIFIC FOR THE WEEKEND THROUGH
EARLY NEXT WEEK. WITH A NEARLY ZONAL JET AND ABUNDANT
MOISTURE...EXPECT PLENTY OF RAINFALL TO CONTINUE THROUGH SUNDAY. ON
MONDAY AND TUESDAY...SOME WEAK RIDGING MOVES OVER THE REGION BUT
SHOWERS LIKELY CONTINUE IN THE MOIST ONSHORE FLOW. AN UPPER TROUGH
DROPS SOUTH OVER THE REGION BY MIDWEEK WITH SOME RATHER COLD AIR AND
ADDITIONAL PRECIPITATION IN STORE. WHILE STILL SOME SIGNIFICANT
UNCERTAINTY EXISTS WITH RESPECT TO THE TIMING OF THE PRECIP VS COLD
AIR AND JUST HOW COLD THE AIR IS...IT DOES APPEAR THAT A SIGNIFICANT
SURGE OF COLD AIR MAY MOVE INTO THE REGION AND THEREFORE...DECREASED
TEMPERATURES ACCORDINGLY FOR THE TUE/WED PERIODS ACROSS THE REGION.
IT DOES APPEAR THAT SNOW LEVELS WILL DROP BELOW PASS LEVELS AT
LEAST...AND PERHAPS DOWN INTO THE FOOTHILL ELEVATIONS LATER
WEDNESDAY INTO THURSDAY. GIVEN THE UNCERTAINTY...THOSE PLANNING
HOLIDAY TRAVEL DURING THIS PERIOD SHOULD MONITOR THE FORECAST.
CULLEN

&&

.AVIATION...VFR CONDITIONS LIKELY TO CONTINUE THROUGH THIS
AFTERNOON. ONSHORE WINDS THIS EVENING BEHIND THE WEAK LOW MOVING
ONSHORE WILL ALLOW FOR CIGS AND VIS TO LOWER TO IFR TONIGHT WITH
THE DEVELOPMENT OF FOG/LOW STRATUS. THIS SHOULD HOLD ON THROUGH
THURSDAY MORNING...STARTING TO LIFT BACK TOWARD VFR AROUND 15 TO 18Z
THURSDAY AS WINDS START TO INCREASE OUT OF THE SOUTH. VFR WILL
CONTINUE THROUGH THURSDAY AFTERNOON...THOUGH LOW-LEVEL WIND SHEAR
WILL BE A CONCERN AT KTTD AND POSSIBLY KPDX AS 20 KT EASTERLY
WINDS FROM THE GORGE UNDERCUT INCREASING SOUTHERLY WINDS ALOFT.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST THIS
EVENING. WEAK WINDS WILL COULD PROMOTE THE DEVELOPMENT OF FOG/LOW
STRATUS AFTER 06Z THURSDAY...DROPPING CIGS AND VIS TO IFR. THIS
SHOULD LIFT BACK TO VFR BY 18Z THURSDAY. -MCCOY

&&

.MARINE...WEAK LOW PRESSURE SYSTEM MOVING NORTHWARD ALONG THE
COAST HAS BROUGHT WINDS UP TO SCA CRITERIA THIS AFTERNOON IN OUR
SOUTHERN WATERS. THIS IS WEAKENING AND MOVING ONSHORE...WHICH
SHOULD ALLOW WINDS TO SUBSIDE FOR A BRIEF PERIOD THIS EVENING.
WINDS WILL BEGIN TO INCREASE ACROSS OUR WATERS THURSDAY MORNING
AHEAD OF A COLD FRONT WHICH WILL MOVE THROUGH OUR WATERS DURING
THE DAY THURSDAY. AHEAD OF THIS FRONT...WINDS LIKELY TO RAMP UP TO
GALE FORCE WITH A COASTAL JET FULLY DEVELOPED BY THURSDAY
EVENING AND PERSIST UNTIL THE FRONT MOVES ONSHORE EARLY FRIDAY
MORNING.

SEAS CURRENTLY AROUND 10-12 FT WILL DROP TO 9 FT LATER THIS
EVENING. SEAS WILL BEGIN TO BUILD AGAIN THURSDAY MORNING AS WINDS
INCREASE AHEAD OF THE COLD FRONT ON THURSDAY. SEAS EXPECTED TO
BUILD TO THE LOW-TO-MIDDLE TEENS THURSDAY EVENING...SUBSIDING TO
10 TO 12 FT EARLY FRIDAY MORNING. A DYNAMIC FETCH APPROACHES EARLY
FRIDAY...BRINGING A LARGE SWELL INTO OUR WATERS. THIS WILL CAUSE
SEAS TO RAPIDLY BUILD FRIDAY MORNING...REACHING 20 FT FRIDAY
EVENING. THE NEXT STRONG FRONT APPROACHES ON SATURDAY...WITH
GALES POSSIBLE...COULD BUILD SEAS ALREADY 15 TO 20 FEET...TO 20
TO 25 FT SATURDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO 1 PM PST THURSDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING FROM 1 PM THURSDAY TO MIDNIGHT PST THURSDAY NIGHT
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 1 PM PST THURSDAY FOR
     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 AM PST THURSDAY.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KSEW 172249
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST WED DEC 17 2014

.SYNOPSIS...A WEAK FRONT WILL DISSIPATE OVER THE REGION TONIGHT AND
EARLY THURSDAY. THE NEXT STRONGER PACIFIC FRONTAL SYSTEM WILL MOVE
ASHORE THURSDAY NIGHT WITH MORE SIGNIFICANT RAIN AND SOME MOUNTAIN
SNOW. ANOTHER WET WEATHER SYSTEM IS FORECAST FOR THIS WEEKEND WITH
HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN THE MOUNTAINS. COOLER
AND MORE SHOWERY WEATHER MAY DEVELOP BY THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...MOIST SW FLOW ALOFT CONTINUES OVER THE PAC NW AHEAD OF
AN APPROACHING SPLIT NRN STREAM TROUGH. PRECIPITATION WAS LIGHT
TODAY WITH MOST SPOTS RECEIVING LESS THAN ONE TENTH OF AN INCH. THE
NEXT BATCH OF RAIN WILL ALSO BE LIGHT THIS EVENING WITH JUST MINOR
MEASURABLE AMOUNTS FOR MOST PLACES. SATELLITE IMAGERY SHOWS MORE
PRONOUNCED SPLITTING OF THE FRONTAL BAND STARTING TO MOVE INLAND.
HRRR AND NAM12 MODELS STILL KEEP LIGHT RAIN AROUND THE AREA...AT
LEAST THROUGH THE EVENING HOURS BEFORE DECREASING. WILL MAINTAIN THE
CHANCE POPS WITH MORE UNCERTAINTY THAN USUAL FOR THE FIRST PERIOD
FORECAST.

LIGHT SHOWERS MAY LINGER INTO THURSDAY MORNING BUT AN UPPER LEVEL
RIDGE WILL BE MOVING ACROSS WRN WA DURING THE DAY. THE NAM12 SHOWS
SOME LIGHT SPOTTY QPF OVER THE AREA UNTIL THE NEXT STRONGER FRONTAL
SYSTEM ARRIVES LATER IN THE DAY. CONSIDERATION WAS GIVEN TO DRYING
OUT THE MORNING PERIOD FOR INLAND AREAS BUT GIVEN THE NAM12...SOME
LIGHT PRECIPITATION CANNOT BE RULED OUT AND CHANCE POPS WILL BE
MAINTAINED.

MODELS AGREE THAT RAIN WILL DEVELOP ON THE COAST LATE IN THE DAY
WITH A WEAK WARM FRONTAL FEATURE. THE TRAILING COLD FRONT WILL
QUICKLY FOLLOW...PUSHING THROUGH WRN WA THURSDAY NIGHT. THIS SYSTEM
WILL BRING MORE RAIN THAN PREVIOUS SYSTEMS AND ALSO SOME COOLER AIR
WITH LOWERING SNOW LEVELS. A FEW INCHES OF SNOW ARE STILL EXPECTED
IN THE MOUNTAINS ABOVE ABOVE 4000 FEET ONCE THE SNOW LEVELS DROPS
OFF THURSDAY NIGHT. ABOVE 5500 FEET...UP TO 6 INCHES COULD
FALL...MAINLY ALONG S/SW FACING SLOPES OF MOUNT BAKER AND MOUNT
RAINIER.

RAIN WILL CHANGE OVER TO SHOWERS IN THE LOWLANDS FRIDAY AND SNOW
WILL TAPER OFF IN THE MOUNTAINS. A LULL IN PRECIPITATION IS EXPECTED
BETWEEN STORM SYSTEMS POSSIBLY THROUGH MUCH OF FRIDAY NIGHT BUT
MODELS DIFFER SLIGHTLY ON THE TIMING OF THE NEXT FRONT.

MODELS HOW A STRONG WARM FRONT TO SPREAD RAIN INTO WRN WA BY
SATURDAY MORNING. A MOIST WESTERLY FLOW PATTERN WILL BE DIRECTED
INTO WRN WA/WRN OREGON BY SATURDAY NIGHT AND SUNDAY. THE 12Z ECMWF
HAS TRENDED TOWARD THE PAST 2-3 GFS40 RUNS SAGGING THE MOISTURE PLUM
SWD ON SUNDAY AFTERNOON. THIS WOULD SHIFT HEAVIER MOUNTAIN RAIN INTO
THE CASCADES OF SRN WA/AND OREGON WITH LIGHTER FURTHER N OVER THE
CENTRAL/N WA CASCADES. WHILE MODELS HAVE TRENDED TOWARD LESS
PRECIPITATION OVER THE WA CASCADES THE MODELS HAVE YET TO LATCH ON
TO ONE PARTICULAR SOLUTION SO UNCERTAINTY REMAINS HIGH ON WHERE THE
HEAVIEST RAIN WILL FALL. SEE THE HYDRO DISCUSSION BELOW FOR FURTHER
DETAILS.

.LONG TERM...MODELS NOW SHOW A BREAK OR AT LEAST DECREASE IN
RAINFALL RATES SUNDAY NIGHT AS WEAK HIGH PRESSURE TEMPORARILY BUILDS
OFFSHORE. THE RIDGE WILL LIFT THE FLOW NWD SO MOISTURE DIRECTED INTO
SRN WA/OREGON WILL LIFT BACK OVER WRN WA ON MONDAY. THE RIDGING IS
QUITE A BIT STRONGER ON MOST OF TODAY`S MODEL RUNS WHICH WOULD SHUT
OFF PRECIPITATION BY LATE MONDAY OR MONDAY NIGHT. THE GOOD NEWS IS
THAT IF HEAVY RAIN DOES DEVELOP IT APPEARS THERE WILL BE SOME
SHIFTING BETWEEN THE CASCADES OF WRN WA/WRN OREGON. THIS SHOULD
LIMIT POTENTIAL QPF IN ANY ONE PARTICULAR AREA. MODELS NOW SHOW 24
TO 36 HOUR QPF AMOUNTS OF 4 TO 6 INCHES MORE EVENLY DISTRIBUTED
ALONG THE WA/OREGON CASCADES. THIS IS STILL ENOUGH FOR SOME MINOR
FLOODING ON THE MORE PRONE RIVERS SO FORECASTS SHOULD BE MONITORED
CLOSELY.

ANOTHER SURFACE LOW WILL TRACK INTO WRN WA OR NRN OREGON AROUND
TUESDAY. MODELS NO LONGER TAP THIS LOW FOR A CONTINUOUS MOISTURE
STREAM WHICH INSTEAD ARRIVES AFTER A BREAK IN RAINFALL. MODELS ARE
ALSO TRENDING MUCH WEAKER WITH THIS LOW SO ADDITIONAL RAIN AMOUNTS
LOOK TO BE LIGHT AND NOT HYDROLOGICALLY SIGNIFICANT.

LONG RANGE MODELS ARE INDICATING A POSSIBLE PATTERN CHANGE BY THE
MIDDLE OF NEXT WEEK. HOWEVER...MODELS DIFFER ON THE POSITIONING OF A
HIGH OVER KONA LOW PATTERN OVER THE PACIFIC WHICH WILL DETERMINE THE
STRENGTH OF NLY FLOW OVER WRN WA. THE 12/18Z GFS IS FURTHER E WITH
THE LOW AND DUMPS MOST THE COLD AIR INTO THE ROCKIES. COLDER AIR
WOULD ARRIVE ACROSS WRN WA IF THE ECMWF SOLUTION VERIFIED WITH THE
LOW FURTHER W. EITHER WAY...A TRANSITION TO COOLER TEMPERATURES IS
LIKELY ENOUGH TO TREND HIGH/LOW TEMPS DOWNWARD A BIT FOR WEDNESDAY.
MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY NIGHT AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. THE
LATEST 12Z GFS/ECMWF ARE FASTER WITH THE TRAILING FRONTAL BAND AND
PUSHES IT SWD INTO OREGON BY MONDAY. THIS COULD HELP MITIGATE ANY
RIVER FLOODING THAT DEVELOPS BUT DOES NOT END THE THREAT AS MODELS
HAVE NOT ALL SETTLED ON A PARTICULAR SOLUTION. 24 TO 36 HOUR RAIN
AMOUNTS ARE STILL AVERAGING ABOUT 4 TO 5 INCHES OVER THE WA CASCADES
WHICH COULD CAUSE FLOODING ON PRONE RIVERS. AT THIS TIME...PRIMARY
CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE SKOKOMISH BUT
ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE STREAMS. MERCER

&&

.AVIATION...A STRETCHED OUT AND WEAKENING UPPER LEVEL TROUGH ALONG
THE COAST WILL MOVE ONSHORE TONIGHT. A STRONG PACIFIC FRONT
APPROACHING 140W THIS AFTERNOON WILL APPROACH THE COASTAL WATERS
THURSDAY AFTERNOON. AT THE SURFACE...HIGH PRES E OF THE CASCADES
COMBINED WITH LOWER PRES OVER THE COASTAL WATERS IS GIVING LIGHT
OFFSHORE FLOW. FLOW WILL BECOME LIGHT TO WEAKLY ONSHORE TONIGHT AS
THE TROUGH OFF THE COAST MOVES INLAND. FLOW ALOFT IS LIGHT SWLY AND
IS MOIST AND STABLE.

PACIFIC NW RADARS CONTINUE TO SHOW BANDS OF LIGHT RAIN SHOWERS
EXTENDING FROM THE NORTH INTERIOR SOUTHWESTWARD TO THE NORTHWEST
OREGON COASTAL WATERS. THIS MOISTURE IS MOVING NE AHEAD OF THE
INCOMING WEAKENING TROUGHS OFFSHORE. MOST TERMINALS IN THE INTERIOR
ARE SEEING VFR CEILINGS AND VISIBILITIES DESPITE THE LIGHT RAIN AS A
RESULT OF THE OFFSHORE PRES GRADIENTS. THE EXCEPTIONS ARE ON THE
NORTH COAST WHERE MVFR CONDITIONS ARE OCCURRING AND AT KOLM WHERE
SOME SCT-BKN006 IS PRODUCING OCCASIONAL IFR CONDITIONS THIS
AFTERNOON. WITH PRES GRADIENTS CONTINUING TO RELAX
OVERNIGHT...EXPECT CEILINGS TO BECOME MOSTLY MVFR LATER THIS EVENING
THROUGH THU MORNING. LOCAL IFR CONDITIONS CAN BE EXPECTED IN THE S
INTERIOR LATE TONIGHT INTO THU MORNING. ALBRECHT

KSEA...EXPECT CIGS AROUND 045 THROUGH THIS EVENING WITH PERIODS OF
LIGHT RAIN. CEILINGS WILL FALL TO 015-020 AFTER 05Z THIS EVENING AND
CONTINUE UNTIL 18Z. SOME IMPROVEMENT CAN BE EXPECTED THU AFTERNOON
AS OFFSHORE PRES GRADIENTS INCREASE IN RESPONSE TO THE NEXT
APPROACHING FRONT. LIGHT SE WINDS GENERALLY LESS THAN 6 KT. ALBRECHT

&&

.MARINE...A WEAK TROUGH OF LOW PRES OVER THE COASTAL WATERS WILL
MOVE INLAND OVERNIGHT. EXPECT LIGHT FLOW. SEAS OVER THE COASTAL
WATERS ARE EXPECTED TO DIMINISH TO BELOW 10 FEET LATE THIS
AFTERNOON...SO THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FOR THE
COASTAL WATERS AND THE SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR
BAR WILL BE ALLOWED TO EXPIRE.

A STRONG PACIFIC FRONT ASSOCIATED WITH A 960 MB LOW CENTERED NEAR
50N 156W IS APPROACHING 142W THIS AFTERNOON. THIS FRONT WILL MOVE
THROUGH THE OFFSHORE WATERS ON THU...THEN MOVE INLAND THU NIGHT. A
PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE COASTAL WATERS
THU AFTERNOON THRU THU NIGHT AHEAD OF AND WITH THE FRONT. THE GALE
WATCH FOR THE COASTAL WATERS WAS UPGRADED TO A GALE WARNING. EXPECT
SMALL CRAFT ADVISORY CONDITIONS LATER THURSDAY OR THURSDAY NIGHT AT
THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA...THE NORTHERN INLAND
WATERS...AND ADMIRALTY INLET.

THE FETCH AREA TO THE SOUTH OF THE LOW NEAR 50N 156W IS MOVING WITH
THE WAVE FIELD IT IS PRODUCING. THE WAVEWATCH MODEL CONTINUES TO
FORECAST SEAS NEAR 45 FT TO THE S OF THIS LOW TONIGHT...AND THESE
WAVES ARE EXPECTED TO DECAY INTO AN ENERGETIC 22 FT AT 20 SEC SWELL
ON THE WASHINGTON COAST LATE FRI AFTERNOON AND FRI NIGHT. AS IT
TURNS OUT...TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FT ABOVE
NORMAL AND HIGH TIDE OCCURS SAT MORNING. IF SWELL REMAINS HIGH INTO
SAT MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE ALONG PORTIONS OF THE COASTAL WATERS AROUND HIGH TIDE ON
SATURDAY. IT IS TOO EARLY TO TELL AT THIS POINT AND TOO EARLY TO
ISSUE ANY COASTAL FLOOD WATCHES...BUT INTERESTS ON THE COAST ARE
URGED TO KEEP UP WITH LATEST FORECASTS.

ANOTHER STRONG WARM FRONT WILL ARRIVE ON SAT AND WILL LIKELY RESULT
IN A PERIOD OF GALE FORCE WINDS OVER THE COASTAL WATERS...THE NORTH
INLAND WATERS...AND THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA.
THEN ONSHORE FLOW WILL SLOWLY EASE ON SUN. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COASTAL WATERS UNTIL 4
      PM PST THIS AFTERNOON.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR UNTIL 4 PM
      PST THIS AFTERNOON.
     GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML














000
FXUS66 KSEW 172249
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST WED DEC 17 2014

.SYNOPSIS...A WEAK FRONT WILL DISSIPATE OVER THE REGION TONIGHT AND
EARLY THURSDAY. THE NEXT STRONGER PACIFIC FRONTAL SYSTEM WILL MOVE
ASHORE THURSDAY NIGHT WITH MORE SIGNIFICANT RAIN AND SOME MOUNTAIN
SNOW. ANOTHER WET WEATHER SYSTEM IS FORECAST FOR THIS WEEKEND WITH
HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN THE MOUNTAINS. COOLER
AND MORE SHOWERY WEATHER MAY DEVELOP BY THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...MOIST SW FLOW ALOFT CONTINUES OVER THE PAC NW AHEAD OF
AN APPROACHING SPLIT NRN STREAM TROUGH. PRECIPITATION WAS LIGHT
TODAY WITH MOST SPOTS RECEIVING LESS THAN ONE TENTH OF AN INCH. THE
NEXT BATCH OF RAIN WILL ALSO BE LIGHT THIS EVENING WITH JUST MINOR
MEASURABLE AMOUNTS FOR MOST PLACES. SATELLITE IMAGERY SHOWS MORE
PRONOUNCED SPLITTING OF THE FRONTAL BAND STARTING TO MOVE INLAND.
HRRR AND NAM12 MODELS STILL KEEP LIGHT RAIN AROUND THE AREA...AT
LEAST THROUGH THE EVENING HOURS BEFORE DECREASING. WILL MAINTAIN THE
CHANCE POPS WITH MORE UNCERTAINTY THAN USUAL FOR THE FIRST PERIOD
FORECAST.

LIGHT SHOWERS MAY LINGER INTO THURSDAY MORNING BUT AN UPPER LEVEL
RIDGE WILL BE MOVING ACROSS WRN WA DURING THE DAY. THE NAM12 SHOWS
SOME LIGHT SPOTTY QPF OVER THE AREA UNTIL THE NEXT STRONGER FRONTAL
SYSTEM ARRIVES LATER IN THE DAY. CONSIDERATION WAS GIVEN TO DRYING
OUT THE MORNING PERIOD FOR INLAND AREAS BUT GIVEN THE NAM12...SOME
LIGHT PRECIPITATION CANNOT BE RULED OUT AND CHANCE POPS WILL BE
MAINTAINED.

MODELS AGREE THAT RAIN WILL DEVELOP ON THE COAST LATE IN THE DAY
WITH A WEAK WARM FRONTAL FEATURE. THE TRAILING COLD FRONT WILL
QUICKLY FOLLOW...PUSHING THROUGH WRN WA THURSDAY NIGHT. THIS SYSTEM
WILL BRING MORE RAIN THAN PREVIOUS SYSTEMS AND ALSO SOME COOLER AIR
WITH LOWERING SNOW LEVELS. A FEW INCHES OF SNOW ARE STILL EXPECTED
IN THE MOUNTAINS ABOVE ABOVE 4000 FEET ONCE THE SNOW LEVELS DROPS
OFF THURSDAY NIGHT. ABOVE 5500 FEET...UP TO 6 INCHES COULD
FALL...MAINLY ALONG S/SW FACING SLOPES OF MOUNT BAKER AND MOUNT
RAINIER.

RAIN WILL CHANGE OVER TO SHOWERS IN THE LOWLANDS FRIDAY AND SNOW
WILL TAPER OFF IN THE MOUNTAINS. A LULL IN PRECIPITATION IS EXPECTED
BETWEEN STORM SYSTEMS POSSIBLY THROUGH MUCH OF FRIDAY NIGHT BUT
MODELS DIFFER SLIGHTLY ON THE TIMING OF THE NEXT FRONT.

MODELS HOW A STRONG WARM FRONT TO SPREAD RAIN INTO WRN WA BY
SATURDAY MORNING. A MOIST WESTERLY FLOW PATTERN WILL BE DIRECTED
INTO WRN WA/WRN OREGON BY SATURDAY NIGHT AND SUNDAY. THE 12Z ECMWF
HAS TRENDED TOWARD THE PAST 2-3 GFS40 RUNS SAGGING THE MOISTURE PLUM
SWD ON SUNDAY AFTERNOON. THIS WOULD SHIFT HEAVIER MOUNTAIN RAIN INTO
THE CASCADES OF SRN WA/AND OREGON WITH LIGHTER FURTHER N OVER THE
CENTRAL/N WA CASCADES. WHILE MODELS HAVE TRENDED TOWARD LESS
PRECIPITATION OVER THE WA CASCADES THE MODELS HAVE YET TO LATCH ON
TO ONE PARTICULAR SOLUTION SO UNCERTAINTY REMAINS HIGH ON WHERE THE
HEAVIEST RAIN WILL FALL. SEE THE HYDRO DISCUSSION BELOW FOR FURTHER
DETAILS.

.LONG TERM...MODELS NOW SHOW A BREAK OR AT LEAST DECREASE IN
RAINFALL RATES SUNDAY NIGHT AS WEAK HIGH PRESSURE TEMPORARILY BUILDS
OFFSHORE. THE RIDGE WILL LIFT THE FLOW NWD SO MOISTURE DIRECTED INTO
SRN WA/OREGON WILL LIFT BACK OVER WRN WA ON MONDAY. THE RIDGING IS
QUITE A BIT STRONGER ON MOST OF TODAY`S MODEL RUNS WHICH WOULD SHUT
OFF PRECIPITATION BY LATE MONDAY OR MONDAY NIGHT. THE GOOD NEWS IS
THAT IF HEAVY RAIN DOES DEVELOP IT APPEARS THERE WILL BE SOME
SHIFTING BETWEEN THE CASCADES OF WRN WA/WRN OREGON. THIS SHOULD
LIMIT POTENTIAL QPF IN ANY ONE PARTICULAR AREA. MODELS NOW SHOW 24
TO 36 HOUR QPF AMOUNTS OF 4 TO 6 INCHES MORE EVENLY DISTRIBUTED
ALONG THE WA/OREGON CASCADES. THIS IS STILL ENOUGH FOR SOME MINOR
FLOODING ON THE MORE PRONE RIVERS SO FORECASTS SHOULD BE MONITORED
CLOSELY.

ANOTHER SURFACE LOW WILL TRACK INTO WRN WA OR NRN OREGON AROUND
TUESDAY. MODELS NO LONGER TAP THIS LOW FOR A CONTINUOUS MOISTURE
STREAM WHICH INSTEAD ARRIVES AFTER A BREAK IN RAINFALL. MODELS ARE
ALSO TRENDING MUCH WEAKER WITH THIS LOW SO ADDITIONAL RAIN AMOUNTS
LOOK TO BE LIGHT AND NOT HYDROLOGICALLY SIGNIFICANT.

LONG RANGE MODELS ARE INDICATING A POSSIBLE PATTERN CHANGE BY THE
MIDDLE OF NEXT WEEK. HOWEVER...MODELS DIFFER ON THE POSITIONING OF A
HIGH OVER KONA LOW PATTERN OVER THE PACIFIC WHICH WILL DETERMINE THE
STRENGTH OF NLY FLOW OVER WRN WA. THE 12/18Z GFS IS FURTHER E WITH
THE LOW AND DUMPS MOST THE COLD AIR INTO THE ROCKIES. COLDER AIR
WOULD ARRIVE ACROSS WRN WA IF THE ECMWF SOLUTION VERIFIED WITH THE
LOW FURTHER W. EITHER WAY...A TRANSITION TO COOLER TEMPERATURES IS
LIKELY ENOUGH TO TREND HIGH/LOW TEMPS DOWNWARD A BIT FOR WEDNESDAY.
MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. A
MOIST WESTERLY FLOW PATTERN WILL DEVELOP SATURDAY NIGHT AND CONTINUE
THROUGH SUNDAY NIGHT WITH HEAVY RAIN AT TIMES IN THE MOUNTAINS. THE
LATEST 12Z GFS/ECMWF ARE FASTER WITH THE TRAILING FRONTAL BAND AND
PUSHES IT SWD INTO OREGON BY MONDAY. THIS COULD HELP MITIGATE ANY
RIVER FLOODING THAT DEVELOPS BUT DOES NOT END THE THREAT AS MODELS
HAVE NOT ALL SETTLED ON A PARTICULAR SOLUTION. 24 TO 36 HOUR RAIN
AMOUNTS ARE STILL AVERAGING ABOUT 4 TO 5 INCHES OVER THE WA CASCADES
WHICH COULD CAUSE FLOODING ON PRONE RIVERS. AT THIS TIME...PRIMARY
CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE SKOKOMISH BUT
ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE STREAMS. MERCER

&&

.AVIATION...A STRETCHED OUT AND WEAKENING UPPER LEVEL TROUGH ALONG
THE COAST WILL MOVE ONSHORE TONIGHT. A STRONG PACIFIC FRONT
APPROACHING 140W THIS AFTERNOON WILL APPROACH THE COASTAL WATERS
THURSDAY AFTERNOON. AT THE SURFACE...HIGH PRES E OF THE CASCADES
COMBINED WITH LOWER PRES OVER THE COASTAL WATERS IS GIVING LIGHT
OFFSHORE FLOW. FLOW WILL BECOME LIGHT TO WEAKLY ONSHORE TONIGHT AS
THE TROUGH OFF THE COAST MOVES INLAND. FLOW ALOFT IS LIGHT SWLY AND
IS MOIST AND STABLE.

PACIFIC NW RADARS CONTINUE TO SHOW BANDS OF LIGHT RAIN SHOWERS
EXTENDING FROM THE NORTH INTERIOR SOUTHWESTWARD TO THE NORTHWEST
OREGON COASTAL WATERS. THIS MOISTURE IS MOVING NE AHEAD OF THE
INCOMING WEAKENING TROUGHS OFFSHORE. MOST TERMINALS IN THE INTERIOR
ARE SEEING VFR CEILINGS AND VISIBILITIES DESPITE THE LIGHT RAIN AS A
RESULT OF THE OFFSHORE PRES GRADIENTS. THE EXCEPTIONS ARE ON THE
NORTH COAST WHERE MVFR CONDITIONS ARE OCCURRING AND AT KOLM WHERE
SOME SCT-BKN006 IS PRODUCING OCCASIONAL IFR CONDITIONS THIS
AFTERNOON. WITH PRES GRADIENTS CONTINUING TO RELAX
OVERNIGHT...EXPECT CEILINGS TO BECOME MOSTLY MVFR LATER THIS EVENING
THROUGH THU MORNING. LOCAL IFR CONDITIONS CAN BE EXPECTED IN THE S
INTERIOR LATE TONIGHT INTO THU MORNING. ALBRECHT

KSEA...EXPECT CIGS AROUND 045 THROUGH THIS EVENING WITH PERIODS OF
LIGHT RAIN. CEILINGS WILL FALL TO 015-020 AFTER 05Z THIS EVENING AND
CONTINUE UNTIL 18Z. SOME IMPROVEMENT CAN BE EXPECTED THU AFTERNOON
AS OFFSHORE PRES GRADIENTS INCREASE IN RESPONSE TO THE NEXT
APPROACHING FRONT. LIGHT SE WINDS GENERALLY LESS THAN 6 KT. ALBRECHT

&&

.MARINE...A WEAK TROUGH OF LOW PRES OVER THE COASTAL WATERS WILL
MOVE INLAND OVERNIGHT. EXPECT LIGHT FLOW. SEAS OVER THE COASTAL
WATERS ARE EXPECTED TO DIMINISH TO BELOW 10 FEET LATE THIS
AFTERNOON...SO THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FOR THE
COASTAL WATERS AND THE SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR
BAR WILL BE ALLOWED TO EXPIRE.

A STRONG PACIFIC FRONT ASSOCIATED WITH A 960 MB LOW CENTERED NEAR
50N 156W IS APPROACHING 142W THIS AFTERNOON. THIS FRONT WILL MOVE
THROUGH THE OFFSHORE WATERS ON THU...THEN MOVE INLAND THU NIGHT. A
PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE COASTAL WATERS
THU AFTERNOON THRU THU NIGHT AHEAD OF AND WITH THE FRONT. THE GALE
WATCH FOR THE COASTAL WATERS WAS UPGRADED TO A GALE WARNING. EXPECT
SMALL CRAFT ADVISORY CONDITIONS LATER THURSDAY OR THURSDAY NIGHT AT
THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA...THE NORTHERN INLAND
WATERS...AND ADMIRALTY INLET.

THE FETCH AREA TO THE SOUTH OF THE LOW NEAR 50N 156W IS MOVING WITH
THE WAVE FIELD IT IS PRODUCING. THE WAVEWATCH MODEL CONTINUES TO
FORECAST SEAS NEAR 45 FT TO THE S OF THIS LOW TONIGHT...AND THESE
WAVES ARE EXPECTED TO DECAY INTO AN ENERGETIC 22 FT AT 20 SEC SWELL
ON THE WASHINGTON COAST LATE FRI AFTERNOON AND FRI NIGHT. AS IT
TURNS OUT...TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FT ABOVE
NORMAL AND HIGH TIDE OCCURS SAT MORNING. IF SWELL REMAINS HIGH INTO
SAT MORNING AS CURRENTLY EXPECTED...SOME COASTAL FLOODING IS
POSSIBLE ALONG PORTIONS OF THE COASTAL WATERS AROUND HIGH TIDE ON
SATURDAY. IT IS TOO EARLY TO TELL AT THIS POINT AND TOO EARLY TO
ISSUE ANY COASTAL FLOOD WATCHES...BUT INTERESTS ON THE COAST ARE
URGED TO KEEP UP WITH LATEST FORECASTS.

ANOTHER STRONG WARM FRONT WILL ARRIVE ON SAT AND WILL LIKELY RESULT
IN A PERIOD OF GALE FORCE WINDS OVER THE COASTAL WATERS...THE NORTH
INLAND WATERS...AND THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA.
THEN ONSHORE FLOW WILL SLOWLY EASE ON SUN. ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COASTAL WATERS UNTIL 4
      PM PST THIS AFTERNOON.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR UNTIL 4 PM
      PST THIS AFTERNOON.
     GALE WARNING THURSDAY AND THURSDAY NIGHT COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML















000
FXUS66 KPQR 171756
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
954 AM PST WED DEC 17 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND EVENTUALLY MOVE ONSHORE ALONG THE N OR/S WA COAST
THIS AFTERNOON. THIS WILL MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY
OVER THE HIGHER TERRAIN THIS MORNING. AN UPPER LEVEL SHORTWAVE WILL
PUSH ONSHORE LATER TODAY...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST AND RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.UPDATE...SUBTLE CHANGES FOR TODAY MAINLY BY INCREASING POPS FOR THE
AFTERNOON...AND LATE AFTERNOON PROBABLY IN REALITY. ALSO PLAN ON
RAMPING UP COAST RANGE AND CASCADE WINDS FOR THE NEXT FRONTAL SYSTEM
MAINLY LATE THURSDAY AFTERNOON AND THURSDAY NIGHT. NOT ANTICIPATING
ANY HIGHLIGHTS BUT PROBABLY A RUN OF THE MILL WINDY COASTAL STORM.

MAIN ATTENTION WILL BE PLACED ON THE ATMOSPHERIC RIVER EVENT SETTING
UP TO AFFECT THE REGION THIS WEEKEND WITH IMPACTS LASTING INTO NEXT
WEEK. RAW GFS MODEL RUN ACCUMULATED QPF AMOUNTS EXCEED 12 INCHES FOR
PORTIONS OF THE CASCADES AND 10 INCHES FOR THE COAST RANGE ENDING
MONDAY MORNING. MOST OF THAT OCCURS BEGINNING SATURDAY. THERE WOULD
BE DEEP WESTERLY FLOW FROM THE SURFACE UP TO THE JET LEVEL THUS
EXPECT THIS COULD BE AN IDEAL SITUATION TO EXTRACT A MAXIMUM AMOUNT
OF RAIN FROM WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE
SUPPORT FROM THE ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS
FOLLOWING THE HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT
REALITY BRINGS SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL
RUNS STAY UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM
RIVERS EXCEEDING FLOOD STAGE AS SOON AS SUNDAY MORNING.

WILL BEGIN TO ISSUE SOME OUTLOOK PRODUCTS TODAY WITH THE CAVEAT THAT
MODELS HAVE RELATIVELY RECENTLY SHIFTED THE FOCUS FROM NORTHERN
WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA. ADDITIONAL SHIFTING
IS EXPECTED AS WELL AS TIMING DIFFERENCES. STAY TUNED AS THIS
SITUATION EVOLVES OVER TIME. /JBONK

&&

.PREV DISC... /ISSUED 259 AM PST WED DEC 17 2014/

SHORT TERM...TODAY THROUGH SATURDAY...VERY LIGHT RAIN CONTINUES TO
IMPACT SW WASHINGTON THIS MORNING BUT HAS OTHERWISE STARTED TO
DISSIPATE OVER THE SOUTHERN PORTION OF THE FORECAST AREA. WATER
VAPOR IMAGERY SHOWS A CLOSED LOW WEAKENING AS IT HAS PUSHED ONSHORE
NEAR THE OREGON/CALIFORNIA BORDER...WHILE AN UPPER LEVEL SHORTWAVE
IS ELONGATING AS IT APPROACHES THE PACIFIC NORTHWEST COASTLINE. NOT
MUCH CHANGE IN THE KTTD-KDLS GRADIENT...WHICH REMAINS AROUND -5
EARLY THIS MORNING. EAST WINDS CONTINUE TO GUST NEAR 25 MPH THROUGH
THE GORGE...BUT EXPECT THE EASTERLY GRADIENT TO WEAKEN BY LATE
TONIGHT.

AFTER A PERIOD OF LIGHT RAIN THIS MORNING...MODELS REMAIN CONSISTENT
IN SHOWING AN UPTICK IN PRECIP BY THIS AFTERNOON ASSOCIATED WITH THE
VORT MAX JUST OFFSHORE AROUND 45N 134W. THE LOWER LEVEL MOISTURE
ASSOCIATED WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING
FROM THE SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP THIS
EVENING AND THROUGH TONIGHT. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY.

WITH CLEARING SKIES AND LIGHT WINDS...SHOULD SEE SOME SHALLOW FOG TO
DEVELOP IN INTERIOR VALLEYS TONIGHT THROUGH EARLY THU MORNING. MODELS
MAINTAIN A THREAT FOR LIGHT PRECIP OVER THE HIGHER TERRAIN MUCH OF
THU...BUT OTHERWISE EXPECT DRY CONDITIONS TO PERSIST TO LOWER
ELEVATIONS. THE NEXT SIGNIFICANT FRONTAL SYSTEM ARRIVES LATE
THU...SPREADING RAIN AND BRINGING GUSTY COASTAL WINDS TO THE REGION
THROUGH FRI. PRECIPITABLE WATER IS EXPECTED TO BE NEAR AN INCH AND AN
APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND EXPECT THE
HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE COAST AND COAST
RANGE THROUGH MIDDAY FRI. OTHER LOCATIONS WILL SEE ON AVERAGE 0.5
INCHES OF RAIN. SNOW LEVELS SHOULD REMAIN ABOVE 5000 FEET DURING THE
PEAK RAIN PERIOD...BUT LOWER TO NEAR OR BELOW THE CASCADE PASSES
BEHIND THE FRONT FRIDAY AFTERNOON.

STRONG LOW PRESSURE OVER THE GULF OF ALASKA WILL PUSH INLAND LATE FRI
INTO EARLY SAT MORNING...SIMULTANEOUSLY FLATTENING A BROAD AREA OF
HIGH PRESSURE OVER THE EASTERN PACIFIC. THERE IS INCREASING
CONFIDENCE AN ATMOSPHERIC RIVER SCENARIO WILL SET UP...WITH ABUNDANT
MOISTURE AIMED DIRECTLY AT THE PACIFIC NORTHWEST SAT.

LONG TERM...SATURDAY NIGHT THROUGH TUESDAY...AS THIS TROUGH MOVES ON
SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES ONSHORE AND STALLS
EAST-TO-WEST ACROSS NORTHWEST OREGON AND SOUTHWEST WASHINGTON. THIS
PUTS OUR AREA IN THE PATH OF RAIN STARTING SATURDAY THROUGH MONDAY.
SOME UNCERTAINTY EXISTS IN WHERE THIS BOUNDARY WILL SET UP...WHICH
WILL DETERMINE HOW MUCH RAINFALL WE WILL GET. ON TUESDAY...GEFS
ENSEMBLE SPAGHETTI PLOTS GET MESSY AND SIGNIFICANT DIFFERENCES START
TO SHOW UP BETWEEN THE GFS AND ECMWF...DECREASING CONFIDENCE ON HOW
THE REST OF THE WEEK WILL SHAPE UP.  AS OF NOW...THE MOST COMMON
SOLUTION IS THAT HIGH PRESSURE RIDGING WILL START TO BUILD BACK OVER
THE WESTERN U.S. WHICH SUGGESTS DRIER WEATHER STARTING TUESDAY...
THOUGH UNCERTAINTY IS VERY HIGH. -MCCOY

&&

.AVIATION...VFR CONDITIONS TO PERSIST AT MOST TAF SITES THROUGH
THIS AFTERNOON. AS SHOWERS MOVE IN...THERE MAY BE PERIODS OF
MVFR...ESPECIALLY AT SOUTH WILLAMETTE VALLEY SITES. CLEARING IS
POSSIBLE THIS EVENING...ALLOWING FOG TO DEVELOP IFR CIGS AND
VIS...BUT UNCERTAINTY IS HIGH BECAUSE THE MODELS ARE HINTING AT A
WEAK LOW PRESSURE SYSTEM OFF THE SOUTH OREGON COAST MOVING INLAND
THIS EVENING. THIS COULD BRING ADDITIONAL SHOWERS AND WINDS WHICH
WOULD KEEP CIGS VFR/MVFR. IF ANY CLEARING DOES OCCUR...EXPECT CIGS
AND VIS TO DROP TO IFR WITH THE DEVELOPMENT OF FOG/LOW STRATUS.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST WEDNESDAY.
RAIN MAY BRING PERIODS OF MVFR CIGS AND VIS. CIGS COULD DROP TO
IFR TONIGHT WITH THE DEVELOPMENT OF FOG/LOW STRATUS AFTER 09Z
THURSDAY. -MCCOY

&&

.MARINE...WEST SWELL AROUND 10 FT BRINGING SEAS UP TO SMALL CRAFT
CRITERIA TODAY. SEAS DROP BELOW 10 FT LATER THIS EVENING. THE
SYSTEM OF INTEREST WILL BE TOMORROW WHICH WILL LIKELY BRING
SOUTHERLY GALES THROUGH EARLY FRIDAY. THERE IS STILL SOME
UNCERTAINTY ON TIMING...BUT MODELS ARE COMING INTO AGREEMENT THAT
WINDS WILL START TO INCREASE EARLY THURSDAY MORNING...REACHING
GALE FORCE BY EARLY AFTERNOON. SEAS BUILD INTO THE TEENS THURSDAY
AFTERNOON. SEAS DROP BACK DOWN TO 10 TO 12 FT ON FRIDAY AHEAD OF
THE NEXT SYSTEM WHICH WILL BRING SEAS UP EVEN HIGHER ON SATURDAY.

THERE IS STILL UNCERTAINTY ON THE TIMING OF THE SATURDAY SYSTEM...BUT
AS OF NOW MODELS ARE SUGGESTING THAT WINDS COULD AGAIN REACH GALE
FORCE EARLY SATURDAY...WHICH COULD BUILD SEAS INTO THE LOW 20S.
SEAS START TO FALL EARLY SUNDAY...DROPPING BACK INTO THE LOW
TEENS BY LATE SUNDAY OR EARLY MONDAY. AN ACTIVE WEATHER PATTERN
WILL CONTINUE THROUGH THIS WEEKEND...KEEPING SEAS ELEVATED
THROUGH EARLY NEXT WEEK WITH PERIODS OF GALES POSSIBLE. -MCCOY


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 PM PST THIS AFTERNOON.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 171756
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
954 AM PST WED DEC 17 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND EVENTUALLY MOVE ONSHORE ALONG THE N OR/S WA COAST
THIS AFTERNOON. THIS WILL MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY
OVER THE HIGHER TERRAIN THIS MORNING. AN UPPER LEVEL SHORTWAVE WILL
PUSH ONSHORE LATER TODAY...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST AND RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.UPDATE...SUBTLE CHANGES FOR TODAY MAINLY BY INCREASING POPS FOR THE
AFTERNOON...AND LATE AFTERNOON PROBABLY IN REALITY. ALSO PLAN ON
RAMPING UP COAST RANGE AND CASCADE WINDS FOR THE NEXT FRONTAL SYSTEM
MAINLY LATE THURSDAY AFTERNOON AND THURSDAY NIGHT. NOT ANTICIPATING
ANY HIGHLIGHTS BUT PROBABLY A RUN OF THE MILL WINDY COASTAL STORM.

MAIN ATTENTION WILL BE PLACED ON THE ATMOSPHERIC RIVER EVENT SETTING
UP TO AFFECT THE REGION THIS WEEKEND WITH IMPACTS LASTING INTO NEXT
WEEK. RAW GFS MODEL RUN ACCUMULATED QPF AMOUNTS EXCEED 12 INCHES FOR
PORTIONS OF THE CASCADES AND 10 INCHES FOR THE COAST RANGE ENDING
MONDAY MORNING. MOST OF THAT OCCURS BEGINNING SATURDAY. THERE WOULD
BE DEEP WESTERLY FLOW FROM THE SURFACE UP TO THE JET LEVEL THUS
EXPECT THIS COULD BE AN IDEAL SITUATION TO EXTRACT A MAXIMUM AMOUNT
OF RAIN FROM WHATEVER COMES ASHORE. THERE IS GENERAL LARGE SCALE
SUPPORT FROM THE ECMWF ALBEIT WITH LESS QPF. PAST EXPERIENCE SHOWS
FOLLOWING THE HIGHER GFS QPF AMOUNTS IS STILL NOT ENOUGH AND THAT
REALITY BRINGS SIGNIFICANTLY MORE RAIN. ASSUMING THE CURRENT MODEL
RUNS STAY UNCHANGED IN THE FUTURE...WOULD EXPECT MULTIPLE MAINSTEM
RIVERS EXCEEDING FLOOD STAGE AS SOON AS SUNDAY MORNING.

WILL BEGIN TO ISSUE SOME OUTLOOK PRODUCTS TODAY WITH THE CAVEAT THAT
MODELS HAVE RELATIVELY RECENTLY SHIFTED THE FOCUS FROM NORTHERN
WASHINGTON/BRITISH COLUMBIA SOUTH TO OUR AREA. ADDITIONAL SHIFTING
IS EXPECTED AS WELL AS TIMING DIFFERENCES. STAY TUNED AS THIS
SITUATION EVOLVES OVER TIME. /JBONK

&&

.PREV DISC... /ISSUED 259 AM PST WED DEC 17 2014/

SHORT TERM...TODAY THROUGH SATURDAY...VERY LIGHT RAIN CONTINUES TO
IMPACT SW WASHINGTON THIS MORNING BUT HAS OTHERWISE STARTED TO
DISSIPATE OVER THE SOUTHERN PORTION OF THE FORECAST AREA. WATER
VAPOR IMAGERY SHOWS A CLOSED LOW WEAKENING AS IT HAS PUSHED ONSHORE
NEAR THE OREGON/CALIFORNIA BORDER...WHILE AN UPPER LEVEL SHORTWAVE
IS ELONGATING AS IT APPROACHES THE PACIFIC NORTHWEST COASTLINE. NOT
MUCH CHANGE IN THE KTTD-KDLS GRADIENT...WHICH REMAINS AROUND -5
EARLY THIS MORNING. EAST WINDS CONTINUE TO GUST NEAR 25 MPH THROUGH
THE GORGE...BUT EXPECT THE EASTERLY GRADIENT TO WEAKEN BY LATE
TONIGHT.

AFTER A PERIOD OF LIGHT RAIN THIS MORNING...MODELS REMAIN CONSISTENT
IN SHOWING AN UPTICK IN PRECIP BY THIS AFTERNOON ASSOCIATED WITH THE
VORT MAX JUST OFFSHORE AROUND 45N 134W. THE LOWER LEVEL MOISTURE
ASSOCIATED WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING
FROM THE SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP THIS
EVENING AND THROUGH TONIGHT. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY.

WITH CLEARING SKIES AND LIGHT WINDS...SHOULD SEE SOME SHALLOW FOG TO
DEVELOP IN INTERIOR VALLEYS TONIGHT THROUGH EARLY THU MORNING. MODELS
MAINTAIN A THREAT FOR LIGHT PRECIP OVER THE HIGHER TERRAIN MUCH OF
THU...BUT OTHERWISE EXPECT DRY CONDITIONS TO PERSIST TO LOWER
ELEVATIONS. THE NEXT SIGNIFICANT FRONTAL SYSTEM ARRIVES LATE
THU...SPREADING RAIN AND BRINGING GUSTY COASTAL WINDS TO THE REGION
THROUGH FRI. PRECIPITABLE WATER IS EXPECTED TO BE NEAR AN INCH AND AN
APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND EXPECT THE
HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE COAST AND COAST
RANGE THROUGH MIDDAY FRI. OTHER LOCATIONS WILL SEE ON AVERAGE 0.5
INCHES OF RAIN. SNOW LEVELS SHOULD REMAIN ABOVE 5000 FEET DURING THE
PEAK RAIN PERIOD...BUT LOWER TO NEAR OR BELOW THE CASCADE PASSES
BEHIND THE FRONT FRIDAY AFTERNOON.

STRONG LOW PRESSURE OVER THE GULF OF ALASKA WILL PUSH INLAND LATE FRI
INTO EARLY SAT MORNING...SIMULTANEOUSLY FLATTENING A BROAD AREA OF
HIGH PRESSURE OVER THE EASTERN PACIFIC. THERE IS INCREASING
CONFIDENCE AN ATMOSPHERIC RIVER SCENARIO WILL SET UP...WITH ABUNDANT
MOISTURE AIMED DIRECTLY AT THE PACIFIC NORTHWEST SAT.

LONG TERM...SATURDAY NIGHT THROUGH TUESDAY...AS THIS TROUGH MOVES ON
SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES ONSHORE AND STALLS
EAST-TO-WEST ACROSS NORTHWEST OREGON AND SOUTHWEST WASHINGTON. THIS
PUTS OUR AREA IN THE PATH OF RAIN STARTING SATURDAY THROUGH MONDAY.
SOME UNCERTAINTY EXISTS IN WHERE THIS BOUNDARY WILL SET UP...WHICH
WILL DETERMINE HOW MUCH RAINFALL WE WILL GET. ON TUESDAY...GEFS
ENSEMBLE SPAGHETTI PLOTS GET MESSY AND SIGNIFICANT DIFFERENCES START
TO SHOW UP BETWEEN THE GFS AND ECMWF...DECREASING CONFIDENCE ON HOW
THE REST OF THE WEEK WILL SHAPE UP.  AS OF NOW...THE MOST COMMON
SOLUTION IS THAT HIGH PRESSURE RIDGING WILL START TO BUILD BACK OVER
THE WESTERN U.S. WHICH SUGGESTS DRIER WEATHER STARTING TUESDAY...
THOUGH UNCERTAINTY IS VERY HIGH. -MCCOY

&&

.AVIATION...VFR CONDITIONS TO PERSIST AT MOST TAF SITES THROUGH
THIS AFTERNOON. AS SHOWERS MOVE IN...THERE MAY BE PERIODS OF
MVFR...ESPECIALLY AT SOUTH WILLAMETTE VALLEY SITES. CLEARING IS
POSSIBLE THIS EVENING...ALLOWING FOG TO DEVELOP IFR CIGS AND
VIS...BUT UNCERTAINTY IS HIGH BECAUSE THE MODELS ARE HINTING AT A
WEAK LOW PRESSURE SYSTEM OFF THE SOUTH OREGON COAST MOVING INLAND
THIS EVENING. THIS COULD BRING ADDITIONAL SHOWERS AND WINDS WHICH
WOULD KEEP CIGS VFR/MVFR. IF ANY CLEARING DOES OCCUR...EXPECT CIGS
AND VIS TO DROP TO IFR WITH THE DEVELOPMENT OF FOG/LOW STRATUS.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST WEDNESDAY.
RAIN MAY BRING PERIODS OF MVFR CIGS AND VIS. CIGS COULD DROP TO
IFR TONIGHT WITH THE DEVELOPMENT OF FOG/LOW STRATUS AFTER 09Z
THURSDAY. -MCCOY

&&

.MARINE...WEST SWELL AROUND 10 FT BRINGING SEAS UP TO SMALL CRAFT
CRITERIA TODAY. SEAS DROP BELOW 10 FT LATER THIS EVENING. THE
SYSTEM OF INTEREST WILL BE TOMORROW WHICH WILL LIKELY BRING
SOUTHERLY GALES THROUGH EARLY FRIDAY. THERE IS STILL SOME
UNCERTAINTY ON TIMING...BUT MODELS ARE COMING INTO AGREEMENT THAT
WINDS WILL START TO INCREASE EARLY THURSDAY MORNING...REACHING
GALE FORCE BY EARLY AFTERNOON. SEAS BUILD INTO THE TEENS THURSDAY
AFTERNOON. SEAS DROP BACK DOWN TO 10 TO 12 FT ON FRIDAY AHEAD OF
THE NEXT SYSTEM WHICH WILL BRING SEAS UP EVEN HIGHER ON SATURDAY.

THERE IS STILL UNCERTAINTY ON THE TIMING OF THE SATURDAY SYSTEM...BUT
AS OF NOW MODELS ARE SUGGESTING THAT WINDS COULD AGAIN REACH GALE
FORCE EARLY SATURDAY...WHICH COULD BUILD SEAS INTO THE LOW 20S.
SEAS START TO FALL EARLY SUNDAY...DROPPING BACK INTO THE LOW
TEENS BY LATE SUNDAY OR EARLY MONDAY. AN ACTIVE WEATHER PATTERN
WILL CONTINUE THROUGH THIS WEEKEND...KEEPING SEAS ELEVATED
THROUGH EARLY NEXT WEEK WITH PERIODS OF GALES POSSIBLE. -MCCOY


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 9 PM PST THIS
     EVENING FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 PM PST THIS AFTERNOON.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.



000
FXUS66 KOTX 171736
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
936 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.

&&

.DISCUSSION...
Quick update to increase pops and snow amounts for Wenatchee and
Waterville Plateau area as radar likly missing the stronger
returns as snow falls from lower cloud deck in that area. The wave
is weak and moving northeast. /Pelatti

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 / 100  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 171736
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
936 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.

&&

.DISCUSSION...
Quick update to increase pops and snow amounts for Wenatchee and
Waterville Plateau area as radar likly missing the stronger
returns as snow falls from lower cloud deck in that area. The wave
is weak and moving northeast. /Pelatti

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 / 100  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 171736
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
936 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.

&&

.DISCUSSION...
Quick update to increase pops and snow amounts for Wenatchee and
Waterville Plateau area as radar likly missing the stronger
returns as snow falls from lower cloud deck in that area. The wave
is weak and moving northeast. /Pelatti

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 / 100  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 171736
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
936 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.

&&

.DISCUSSION...
Quick update to increase pops and snow amounts for Wenatchee and
Waterville Plateau area as radar likly missing the stronger
returns as snow falls from lower cloud deck in that area. The wave
is weak and moving northeast. /Pelatti

&&

.AVIATION...
18Z TAFS: Weak disturbances drifting northeast and over the
aviation over the next 24 hours keep the forecast somewhat
cluttered with mentions of both rain and snow at times which
produce IFR/LIFR ceilings and visibilities. Some fog will
occasionally impact locations as well. Precipitation still on the
light side with the higher amounts primarily near the East Slopes
of the North Cascades out to the Waterville Plateau and points to
the north/northeast. The KGEG area will be more MVFR most of the
time as the precipitation will be light and likely to be rain.
/Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 / 100  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KSEW 171713
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST WED DEC 17 2014

.SYNOPSIS...A WEAK PACIFIC WEATHER SYSTEM WILL BRING SOME AREAS OF
LIGHT RAIN TO WESTERN WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER
PACIFIC FRONTAL SYSTEM IS EXPECTED TO MOVE ASHORE THURSDAY NIGHT
WITH MORE SIGNIFICANT RAIN. ANOTHER WET WEATHER SYSTEM IS FORECAST
FOR THIS WEEKEND WITH HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN
THE MOUNTAINS.

&&

.SHORT TERM...MODELS ARE NOT HANDLING THE NRN STREAM PORTION OF THE
SPLIT TROUGH AFFECTING WRN WA ALL THAT WELL. THE ELONGATED 500 MB
TROUGH AXIS IS OFFSHORE JUST INSIDE 130 W AND THERE IS STILL SOME
SURFACE STRUCTURE LEFT ACCORDING THE HRRR WHICH MOST MODELS DO NOT
SHOW. THE HRRR FROM YESTERDAY AFTERNOON IS THE WINNER WHICH WAS
SHOWING SLY FLOW ENTRAINING SOME MOISTURE FROM THE SRN STREAM SYSTEM
INTO WRN WA EARLY THIS MORNING. RADAR NOW SHOWS LIGHT RAIN AROUND
MUCH OF WRN WA INCLUDING PUGET SOUND. SOME MODELS LIKE THE GFS40
WERE MOSTLY DRY AND STILL SHOW ONLY LIGHT QPF FIELDS W OF THE SOUND
AND ACROSS THE FAR N AND CASCADES. THE HRRR DOES DRY OUT THE
INTERIOR BY LATE MORNING BEFORE SPREADING SOME LIGHT RAIN BACK INTO
THE AREA EARLY THIS EVENING LIKE THE NAM12 SHOWS. THIS TIMING IS
QUESTIONABLE GIVEN THE BRIGHT CLOUDS ON IR IMAGERY APPROACHING THE
COAST COUPLED WITH THE LANGLEY HILL RADAR SHOWING MORE RAIN BANDS
ALONG THE COAST LIFTING NE. WILL MAINTAIN THE CURRENT LIKELY POPS
FOR TODAY AND TONIGHT.

THE 500 MB TROUGH AXIS FINALLY SHIFTS E OF THE AREA BY 12Z THURSDAY
MORNING. WITH LIGHT FLOW AND A SHORT WAVE RIDGE TRAVERSING THE
AREA...EXPECT LOW CLOUDS AND MAYBE SOME FOG AROUND THE AREA. THIS
WILL BREAK UP BY MIDDAY AS THE NEXT STRONGER FRONT APPROACHES
INCREASING THE FLOW OUT AHEAD OF IT. TIMING IS STILL TRICKY WITH THE
06Z GFS BRINGING RAIN AS FAR INLAND AS THE WRN PORTION OF PUGET
SOUND BY LATE THURSDAY AFTERNOON. THE NAM12/ECMWF ARE SIMILAR BUT
THE CANADIAN IS STILL RUNNING A FEW HOURS FASTER WITH RAIN
OVERSPREADING WRN WA EARLIER IN THE AFTERNOON. WILL LEAVE POPS
UNCHANGED FOR NOW BUT MAY CONSIDER REMOVING SOME OF THE INTERIOR
POPS FOR A DRY PERIOD THURSDAY MORNING. THIS WOULD PROBABLY RESULT
IN MORE FOG AROUND THE AREA.

THE WARM FRONT MOVES THROUGH QUICKLY WITH COLDER AIR ARRIVING WITH
THE MAIN FRONTAL BAND SLATED FOR THURSDAY NIGHT. THIS SYSTEM APPEARS
TO SPLIT LESS THAN PREVIOUS FRONTS AND THE SE GRADIENTS ARE TIGHT
OVER THE AREA SO EXPECT LOCALLY WINDY CONDITIONS NORTH OF PUGET
SOUND AND ALONG THE COAST. SNOW LEVELS WILL FALL FROM NEAR 5000 FEET
TO 3000 TO 3500 FEET BY LATER THURSDAY NIGHT AND FRIDAY MORNING.
THERE IS A 6 HOUR WINDOW OF STRONGER FLOW ALONG AND BEHIND THE FRONT
WHICH COULD SQUEEZE OUT SEVERAL INCHES OF SNOW EVEN DOWN TO SOME OF
THE PASSES. SKI RESORTS COULD POSSIBLY GET CLOSE TO 6 INCHES OF SNOW
WHICH IS BORDERLINE ADVISORY CRITERIA. MOUNT BAKER MAY GET THE
HIGHER AMOUNTS IN THIS PATTERN. PRECIPITATION WILL FALL AS JUST RAIN
IN THE LOWLANDS...CHANGING TO SHOWERS DURING THE AFTERNOON. ANY
BREAK IN PRECIPITATION WILL AGAIN BE SHORT LIVED AS A STRONG 180+ KT
JET ACROSS THE PACIFIC DRIVES WETTER STORMS TOWARD THE AREA BY
SATURDAY.  MERCER

.LONG TERM...NO UPDATES FROM PREVIOUS DISCUSSION...LOOKS LIKE A
SHORT BREAK IN THE WEATHER FRIDAY NIGHT BEFORE THE NEXT WETTER
SYSTEM ARRIVES OVER THE WEEKEND. THIS SYSTEM WAS CURRENTLY MOVING
ACROSS 150E THIS MORNING WITH A SUPPORTING 200 KT JET. THE PROGS ARE
STILL TRENDING A BIT DRIER WITH THIS SYSTEM GIVEN ITS MORE
PROGRESSIVE NATURE. EXPECT RAIN TO INCREASE ON SATURDAY WITH THE
WARM FRONT AND THE COLD FRONT MOVING ONSHORE SUNDAY NIGHT.

RIDGING ALOFT ALONG THE WEST COAST MEANS THE JET STREAM WILL BE AT
OUR LATITUDE WITH A WESTERLY COMPONENT INTO THE CASCADES AND
SHADOWING OFF THE OLYMPICS THIS WEEKEND. THE COAST AND MOUNTAINS
SHOULD GET THE BULK OF THE PRECIPITATION.

ANOTHER SHORT BREAK MONDAY BEFORE THE NEXT NOT AS WET SYSTEM ARRIVES
TUESDAY. THE PROGS CONTINUE TO SUGGEST A KONA LOW DEVELOPING BUT
THEY ARE INCONSISTENT IN ITS POSITION. THE FURTHER WEST USUALLY
RESULTS IN BUILDING AN UPPER RIDGE NEAR 150W OR 160W AND PRODUCING
NORTHERLY FLOW ALOFT INTO THE PACIFIC NW FOR A MUCH COOLER FLOW
PATTERN. FURTHER EAST WITH THE PATTERN AND THE PACIFIC NW GETS A
MILDER NORTHERLY FLOW ALOFT. STAY TUNED HERE. BUEHNER

&&

.HYDROLOGY...NO UPDATES FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH SATURDAY. MOIST WESTERLY FLOW WILL DEVELOP
SATURDAY NIGHT AND CONTINUE THROUGH SUNDAY NIGHT...WITH HEAVY
MOUNTAIN RAIN AMOUNTS POSSIBLE. GUIDANCE IS NOW SHOWING A BIT
LIGHTER AMOUNTS GIVEN THE MORE PROGRESSIVE NATURE OF THIS SYSTEM.
PRIMARY CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE
SKOKOMISH BUT ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE
STREAMS. BUEHNER

&&

.AVIATION...A STRETCHED OUT AND WEAKENING UPPER LEVEL TROUGH ALONG
THE COAST IS MOVING ONSHORE THIS MORNING AND WILL BE FOLLOWED BY
ANOTHER ONE...CURRENTLY ALONG 132W...TONIGHT. AT THE SURFACE...HIGH
PRES E OF THE CASCADES COMBINED WITH LOWER PRES OVER THE COASTAL
WATERS IS GIVING LIGHT OFFSHORE FLOW. THE AIR MASS IS MOIST AND
STABLE WITH LIGHT S TO SW FLOW ALOFT.

PACIFIC NW RADARS SHOW BANDS OF LIGHT RAIN EXTENDING SW FROM WESTERN
WASHINGTON INTO THE OREGON COASTAL WATERS. THIS MOISTURE IS MOVING
NE AHEAD OF THE INCOMING WEAKENING TROUGHS OFFSHORE. MOST
TERMINALS IN THE INTERIOR ARE SEEING VFR CEILINGS AND VISIBILITIES
DESPITE THE LIGHT RAIN AS A RESULT OF THE OFFSHORE PRES GRADIENTS.
THE EXCEPTIONS ARE AT KCLM WHERE PRECIPITATION AND FLOW MOVING ONTO
THE NORTH SLOPES OF THE OLYMPICS IS PRODUCING A LOWER STRATUS DECK
AND AROUND KOLM WHERE PRECIPITATION IN THE MORE TRAPPED SOUTHWEST
INTERIOR IS PRODUCING LOW IFR STRATUS AND VIS 3-5SM BR.

THE OFFSHORE PRES GRADIENTS ARE EXPECTED TO SLOWLY RELAX THROUGH
TONIGHT AS THE STRETCHING AND DYING TROUGHS OFFSHORE MOVE INTO THE
AREA. THIS WILL RESULT IN GENERALLY DETERIORATING CEILINGS AND
POORER VISIBILITIES AS WE MOVE INTO THE TONIGHT AND THU MORNING
PERIODS. EXPECT AREAS OF IFR CONDITIONS 06Z-18Z THU AT MANY OF THE
TERMINALS IN WESTERN WASHINGTON. ALBRECHT

KSEA...EXPECT CIGS AROUND 040 THROUGH THIS EVENING WITH PERIODS OF
LIGHT RAIN. CEILINGS WILL FALL TO 008-012 AFTER 05Z THIS EVENING AND
CONTINUE UNTIL 18Z. EXPECT VIS TO GENERALLY REMAIN ABOVE 5SM IN OCNL
-RA. EAST WIND AROUND 5 KT BECOMING SE TONIGHT. ALBRECHT

&&

.MARINE...WEAK TROUGHS OF LOW PRES...ONE OVER THE COASTAL WATERS AND
ANOTHER OVER THE OFFSHORE WATERS...WILL STRETCH OUT AND DIE AS THEY
MOVE INTO THE WATERS THIS AFTERNOON THROUGH TONIGHT. EXPECT LIGHT
OFFSHORE FLOW. WITH SEAS OVER THE COASTAL WATERS REMAINING AROUND 10
FT...THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED INTO
THE NEARSHORE COASTAL WATERS. SEAS WILL SUBSIDE LATE THIS AFTERNOON
AND TONIGHT.

A STRONG PACIFIC FRONT ASSOCIATED WITH A 960 MB LOW CENTERED NEAR
49N 159W WILL APPROACH THE OFFSHORE WATERS ON THU...THEN MOVE INLAND
THU NIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS LATER THU AFTERNOON THRU THU NIGHT AHEAD OF AND WITH
THE FRONT. A GALE WATCH IS IN EFFECT FOR THE COASTAL WATERS FOR THU
AFTERNOON AND NIGHT. THESE WILL LIKELY BE UPGRADED TO WARNINGS THIS
AFTERNOON.

THE FETCH AREA TO THE SOUTH OF THE LOW NEAR 49N 159W IS MOVING WITH
THE WAVE FIELD IT IS PRODUCING. THE WAVEWATCH MODEL CONTINUES TO
FORECAST SEAS 40-45 FT AROUND 47N 150W BY LATE TONIGHT. THESE WAVES
ARE EXPECTED TO DECAY INTO AN ENERGETIC 20-22 FT AT 18-20 SEC SWELL
ON THE WASHINGTON COAST LATE FRI AFTERNOON AND FRI NIGHT. AS IT
TURNS OUT...TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FT ABOVE
NORMAL AND HIGH TIDE OCCURS EARLY SAT MORNING. IF SWELL REMAINS HIGH
INTO SAT MORNING...SOME COASTAL FLOODING IS POSSIBLE ALONG PORTIONS
OF THE COASTAL WATERS. IT IS TOO EARLY TO TELL AT THIS POINT AND TOO
EARLY TO ISSUE ANY COASTAL FLOOD WATCHES...BUT INTERESTS ON THE
COAST ARE URGED TO KEEP UP WITH LATEST FORECASTS.

ANOTHER STRONG WARM FRONT WILL ARRIVE ON SAT AND WILL LIKELY RESULT
IN A PERIOD OF GALE FORCE WINDS OVER THE COASTAL WATERS...THE NORTH
INLAND WATERS...AND THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA.
ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY TODAY FOR HAZARDOUS SEAS COASTAL
      WATERS.
     SMALL CRAFT ADVISORY TODAY FOR ROUGH GRAYS HARBOR BAR.
     GALE WATCH MIDDAY THURSDAY THROUGH LATE THURSDAY NIGHT FOR
      THE COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML











000
FXUS66 KSEW 171713
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST WED DEC 17 2014

.SYNOPSIS...A WEAK PACIFIC WEATHER SYSTEM WILL BRING SOME AREAS OF
LIGHT RAIN TO WESTERN WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER
PACIFIC FRONTAL SYSTEM IS EXPECTED TO MOVE ASHORE THURSDAY NIGHT
WITH MORE SIGNIFICANT RAIN. ANOTHER WET WEATHER SYSTEM IS FORECAST
FOR THIS WEEKEND WITH HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN
THE MOUNTAINS.

&&

.SHORT TERM...MODELS ARE NOT HANDLING THE NRN STREAM PORTION OF THE
SPLIT TROUGH AFFECTING WRN WA ALL THAT WELL. THE ELONGATED 500 MB
TROUGH AXIS IS OFFSHORE JUST INSIDE 130 W AND THERE IS STILL SOME
SURFACE STRUCTURE LEFT ACCORDING THE HRRR WHICH MOST MODELS DO NOT
SHOW. THE HRRR FROM YESTERDAY AFTERNOON IS THE WINNER WHICH WAS
SHOWING SLY FLOW ENTRAINING SOME MOISTURE FROM THE SRN STREAM SYSTEM
INTO WRN WA EARLY THIS MORNING. RADAR NOW SHOWS LIGHT RAIN AROUND
MUCH OF WRN WA INCLUDING PUGET SOUND. SOME MODELS LIKE THE GFS40
WERE MOSTLY DRY AND STILL SHOW ONLY LIGHT QPF FIELDS W OF THE SOUND
AND ACROSS THE FAR N AND CASCADES. THE HRRR DOES DRY OUT THE
INTERIOR BY LATE MORNING BEFORE SPREADING SOME LIGHT RAIN BACK INTO
THE AREA EARLY THIS EVENING LIKE THE NAM12 SHOWS. THIS TIMING IS
QUESTIONABLE GIVEN THE BRIGHT CLOUDS ON IR IMAGERY APPROACHING THE
COAST COUPLED WITH THE LANGLEY HILL RADAR SHOWING MORE RAIN BANDS
ALONG THE COAST LIFTING NE. WILL MAINTAIN THE CURRENT LIKELY POPS
FOR TODAY AND TONIGHT.

THE 500 MB TROUGH AXIS FINALLY SHIFTS E OF THE AREA BY 12Z THURSDAY
MORNING. WITH LIGHT FLOW AND A SHORT WAVE RIDGE TRAVERSING THE
AREA...EXPECT LOW CLOUDS AND MAYBE SOME FOG AROUND THE AREA. THIS
WILL BREAK UP BY MIDDAY AS THE NEXT STRONGER FRONT APPROACHES
INCREASING THE FLOW OUT AHEAD OF IT. TIMING IS STILL TRICKY WITH THE
06Z GFS BRINGING RAIN AS FAR INLAND AS THE WRN PORTION OF PUGET
SOUND BY LATE THURSDAY AFTERNOON. THE NAM12/ECMWF ARE SIMILAR BUT
THE CANADIAN IS STILL RUNNING A FEW HOURS FASTER WITH RAIN
OVERSPREADING WRN WA EARLIER IN THE AFTERNOON. WILL LEAVE POPS
UNCHANGED FOR NOW BUT MAY CONSIDER REMOVING SOME OF THE INTERIOR
POPS FOR A DRY PERIOD THURSDAY MORNING. THIS WOULD PROBABLY RESULT
IN MORE FOG AROUND THE AREA.

THE WARM FRONT MOVES THROUGH QUICKLY WITH COLDER AIR ARRIVING WITH
THE MAIN FRONTAL BAND SLATED FOR THURSDAY NIGHT. THIS SYSTEM APPEARS
TO SPLIT LESS THAN PREVIOUS FRONTS AND THE SE GRADIENTS ARE TIGHT
OVER THE AREA SO EXPECT LOCALLY WINDY CONDITIONS NORTH OF PUGET
SOUND AND ALONG THE COAST. SNOW LEVELS WILL FALL FROM NEAR 5000 FEET
TO 3000 TO 3500 FEET BY LATER THURSDAY NIGHT AND FRIDAY MORNING.
THERE IS A 6 HOUR WINDOW OF STRONGER FLOW ALONG AND BEHIND THE FRONT
WHICH COULD SQUEEZE OUT SEVERAL INCHES OF SNOW EVEN DOWN TO SOME OF
THE PASSES. SKI RESORTS COULD POSSIBLY GET CLOSE TO 6 INCHES OF SNOW
WHICH IS BORDERLINE ADVISORY CRITERIA. MOUNT BAKER MAY GET THE
HIGHER AMOUNTS IN THIS PATTERN. PRECIPITATION WILL FALL AS JUST RAIN
IN THE LOWLANDS...CHANGING TO SHOWERS DURING THE AFTERNOON. ANY
BREAK IN PRECIPITATION WILL AGAIN BE SHORT LIVED AS A STRONG 180+ KT
JET ACROSS THE PACIFIC DRIVES WETTER STORMS TOWARD THE AREA BY
SATURDAY.  MERCER

.LONG TERM...NO UPDATES FROM PREVIOUS DISCUSSION...LOOKS LIKE A
SHORT BREAK IN THE WEATHER FRIDAY NIGHT BEFORE THE NEXT WETTER
SYSTEM ARRIVES OVER THE WEEKEND. THIS SYSTEM WAS CURRENTLY MOVING
ACROSS 150E THIS MORNING WITH A SUPPORTING 200 KT JET. THE PROGS ARE
STILL TRENDING A BIT DRIER WITH THIS SYSTEM GIVEN ITS MORE
PROGRESSIVE NATURE. EXPECT RAIN TO INCREASE ON SATURDAY WITH THE
WARM FRONT AND THE COLD FRONT MOVING ONSHORE SUNDAY NIGHT.

RIDGING ALOFT ALONG THE WEST COAST MEANS THE JET STREAM WILL BE AT
OUR LATITUDE WITH A WESTERLY COMPONENT INTO THE CASCADES AND
SHADOWING OFF THE OLYMPICS THIS WEEKEND. THE COAST AND MOUNTAINS
SHOULD GET THE BULK OF THE PRECIPITATION.

ANOTHER SHORT BREAK MONDAY BEFORE THE NEXT NOT AS WET SYSTEM ARRIVES
TUESDAY. THE PROGS CONTINUE TO SUGGEST A KONA LOW DEVELOPING BUT
THEY ARE INCONSISTENT IN ITS POSITION. THE FURTHER WEST USUALLY
RESULTS IN BUILDING AN UPPER RIDGE NEAR 150W OR 160W AND PRODUCING
NORTHERLY FLOW ALOFT INTO THE PACIFIC NW FOR A MUCH COOLER FLOW
PATTERN. FURTHER EAST WITH THE PATTERN AND THE PACIFIC NW GETS A
MILDER NORTHERLY FLOW ALOFT. STAY TUNED HERE. BUEHNER

&&

.HYDROLOGY...NO UPDATES FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH SATURDAY. MOIST WESTERLY FLOW WILL DEVELOP
SATURDAY NIGHT AND CONTINUE THROUGH SUNDAY NIGHT...WITH HEAVY
MOUNTAIN RAIN AMOUNTS POSSIBLE. GUIDANCE IS NOW SHOWING A BIT
LIGHTER AMOUNTS GIVEN THE MORE PROGRESSIVE NATURE OF THIS SYSTEM.
PRIMARY CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE
SKOKOMISH BUT ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE
STREAMS. BUEHNER

&&

.AVIATION...A STRETCHED OUT AND WEAKENING UPPER LEVEL TROUGH ALONG
THE COAST IS MOVING ONSHORE THIS MORNING AND WILL BE FOLLOWED BY
ANOTHER ONE...CURRENTLY ALONG 132W...TONIGHT. AT THE SURFACE...HIGH
PRES E OF THE CASCADES COMBINED WITH LOWER PRES OVER THE COASTAL
WATERS IS GIVING LIGHT OFFSHORE FLOW. THE AIR MASS IS MOIST AND
STABLE WITH LIGHT S TO SW FLOW ALOFT.

PACIFIC NW RADARS SHOW BANDS OF LIGHT RAIN EXTENDING SW FROM WESTERN
WASHINGTON INTO THE OREGON COASTAL WATERS. THIS MOISTURE IS MOVING
NE AHEAD OF THE INCOMING WEAKENING TROUGHS OFFSHORE. MOST
TERMINALS IN THE INTERIOR ARE SEEING VFR CEILINGS AND VISIBILITIES
DESPITE THE LIGHT RAIN AS A RESULT OF THE OFFSHORE PRES GRADIENTS.
THE EXCEPTIONS ARE AT KCLM WHERE PRECIPITATION AND FLOW MOVING ONTO
THE NORTH SLOPES OF THE OLYMPICS IS PRODUCING A LOWER STRATUS DECK
AND AROUND KOLM WHERE PRECIPITATION IN THE MORE TRAPPED SOUTHWEST
INTERIOR IS PRODUCING LOW IFR STRATUS AND VIS 3-5SM BR.

THE OFFSHORE PRES GRADIENTS ARE EXPECTED TO SLOWLY RELAX THROUGH
TONIGHT AS THE STRETCHING AND DYING TROUGHS OFFSHORE MOVE INTO THE
AREA. THIS WILL RESULT IN GENERALLY DETERIORATING CEILINGS AND
POORER VISIBILITIES AS WE MOVE INTO THE TONIGHT AND THU MORNING
PERIODS. EXPECT AREAS OF IFR CONDITIONS 06Z-18Z THU AT MANY OF THE
TERMINALS IN WESTERN WASHINGTON. ALBRECHT

KSEA...EXPECT CIGS AROUND 040 THROUGH THIS EVENING WITH PERIODS OF
LIGHT RAIN. CEILINGS WILL FALL TO 008-012 AFTER 05Z THIS EVENING AND
CONTINUE UNTIL 18Z. EXPECT VIS TO GENERALLY REMAIN ABOVE 5SM IN OCNL
-RA. EAST WIND AROUND 5 KT BECOMING SE TONIGHT. ALBRECHT

&&

.MARINE...WEAK TROUGHS OF LOW PRES...ONE OVER THE COASTAL WATERS AND
ANOTHER OVER THE OFFSHORE WATERS...WILL STRETCH OUT AND DIE AS THEY
MOVE INTO THE WATERS THIS AFTERNOON THROUGH TONIGHT. EXPECT LIGHT
OFFSHORE FLOW. WITH SEAS OVER THE COASTAL WATERS REMAINING AROUND 10
FT...THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED INTO
THE NEARSHORE COASTAL WATERS. SEAS WILL SUBSIDE LATE THIS AFTERNOON
AND TONIGHT.

A STRONG PACIFIC FRONT ASSOCIATED WITH A 960 MB LOW CENTERED NEAR
49N 159W WILL APPROACH THE OFFSHORE WATERS ON THU...THEN MOVE INLAND
THU NIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS LATER THU AFTERNOON THRU THU NIGHT AHEAD OF AND WITH
THE FRONT. A GALE WATCH IS IN EFFECT FOR THE COASTAL WATERS FOR THU
AFTERNOON AND NIGHT. THESE WILL LIKELY BE UPGRADED TO WARNINGS THIS
AFTERNOON.

THE FETCH AREA TO THE SOUTH OF THE LOW NEAR 49N 159W IS MOVING WITH
THE WAVE FIELD IT IS PRODUCING. THE WAVEWATCH MODEL CONTINUES TO
FORECAST SEAS 40-45 FT AROUND 47N 150W BY LATE TONIGHT. THESE WAVES
ARE EXPECTED TO DECAY INTO AN ENERGETIC 20-22 FT AT 18-20 SEC SWELL
ON THE WASHINGTON COAST LATE FRI AFTERNOON AND FRI NIGHT. AS IT
TURNS OUT...TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FT ABOVE
NORMAL AND HIGH TIDE OCCURS EARLY SAT MORNING. IF SWELL REMAINS HIGH
INTO SAT MORNING...SOME COASTAL FLOODING IS POSSIBLE ALONG PORTIONS
OF THE COASTAL WATERS. IT IS TOO EARLY TO TELL AT THIS POINT AND TOO
EARLY TO ISSUE ANY COASTAL FLOOD WATCHES...BUT INTERESTS ON THE
COAST ARE URGED TO KEEP UP WITH LATEST FORECASTS.

ANOTHER STRONG WARM FRONT WILL ARRIVE ON SAT AND WILL LIKELY RESULT
IN A PERIOD OF GALE FORCE WINDS OVER THE COASTAL WATERS...THE NORTH
INLAND WATERS...AND THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA.
ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY TODAY FOR HAZARDOUS SEAS COASTAL
      WATERS.
     SMALL CRAFT ADVISORY TODAY FOR ROUGH GRAYS HARBOR BAR.
     GALE WATCH MIDDAY THURSDAY THROUGH LATE THURSDAY NIGHT FOR
      THE COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML











000
FXUS66 KSEW 171713
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST WED DEC 17 2014

.SYNOPSIS...A WEAK PACIFIC WEATHER SYSTEM WILL BRING SOME AREAS OF
LIGHT RAIN TO WESTERN WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER
PACIFIC FRONTAL SYSTEM IS EXPECTED TO MOVE ASHORE THURSDAY NIGHT
WITH MORE SIGNIFICANT RAIN. ANOTHER WET WEATHER SYSTEM IS FORECAST
FOR THIS WEEKEND WITH HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN
THE MOUNTAINS.

&&

.SHORT TERM...MODELS ARE NOT HANDLING THE NRN STREAM PORTION OF THE
SPLIT TROUGH AFFECTING WRN WA ALL THAT WELL. THE ELONGATED 500 MB
TROUGH AXIS IS OFFSHORE JUST INSIDE 130 W AND THERE IS STILL SOME
SURFACE STRUCTURE LEFT ACCORDING THE HRRR WHICH MOST MODELS DO NOT
SHOW. THE HRRR FROM YESTERDAY AFTERNOON IS THE WINNER WHICH WAS
SHOWING SLY FLOW ENTRAINING SOME MOISTURE FROM THE SRN STREAM SYSTEM
INTO WRN WA EARLY THIS MORNING. RADAR NOW SHOWS LIGHT RAIN AROUND
MUCH OF WRN WA INCLUDING PUGET SOUND. SOME MODELS LIKE THE GFS40
WERE MOSTLY DRY AND STILL SHOW ONLY LIGHT QPF FIELDS W OF THE SOUND
AND ACROSS THE FAR N AND CASCADES. THE HRRR DOES DRY OUT THE
INTERIOR BY LATE MORNING BEFORE SPREADING SOME LIGHT RAIN BACK INTO
THE AREA EARLY THIS EVENING LIKE THE NAM12 SHOWS. THIS TIMING IS
QUESTIONABLE GIVEN THE BRIGHT CLOUDS ON IR IMAGERY APPROACHING THE
COAST COUPLED WITH THE LANGLEY HILL RADAR SHOWING MORE RAIN BANDS
ALONG THE COAST LIFTING NE. WILL MAINTAIN THE CURRENT LIKELY POPS
FOR TODAY AND TONIGHT.

THE 500 MB TROUGH AXIS FINALLY SHIFTS E OF THE AREA BY 12Z THURSDAY
MORNING. WITH LIGHT FLOW AND A SHORT WAVE RIDGE TRAVERSING THE
AREA...EXPECT LOW CLOUDS AND MAYBE SOME FOG AROUND THE AREA. THIS
WILL BREAK UP BY MIDDAY AS THE NEXT STRONGER FRONT APPROACHES
INCREASING THE FLOW OUT AHEAD OF IT. TIMING IS STILL TRICKY WITH THE
06Z GFS BRINGING RAIN AS FAR INLAND AS THE WRN PORTION OF PUGET
SOUND BY LATE THURSDAY AFTERNOON. THE NAM12/ECMWF ARE SIMILAR BUT
THE CANADIAN IS STILL RUNNING A FEW HOURS FASTER WITH RAIN
OVERSPREADING WRN WA EARLIER IN THE AFTERNOON. WILL LEAVE POPS
UNCHANGED FOR NOW BUT MAY CONSIDER REMOVING SOME OF THE INTERIOR
POPS FOR A DRY PERIOD THURSDAY MORNING. THIS WOULD PROBABLY RESULT
IN MORE FOG AROUND THE AREA.

THE WARM FRONT MOVES THROUGH QUICKLY WITH COLDER AIR ARRIVING WITH
THE MAIN FRONTAL BAND SLATED FOR THURSDAY NIGHT. THIS SYSTEM APPEARS
TO SPLIT LESS THAN PREVIOUS FRONTS AND THE SE GRADIENTS ARE TIGHT
OVER THE AREA SO EXPECT LOCALLY WINDY CONDITIONS NORTH OF PUGET
SOUND AND ALONG THE COAST. SNOW LEVELS WILL FALL FROM NEAR 5000 FEET
TO 3000 TO 3500 FEET BY LATER THURSDAY NIGHT AND FRIDAY MORNING.
THERE IS A 6 HOUR WINDOW OF STRONGER FLOW ALONG AND BEHIND THE FRONT
WHICH COULD SQUEEZE OUT SEVERAL INCHES OF SNOW EVEN DOWN TO SOME OF
THE PASSES. SKI RESORTS COULD POSSIBLY GET CLOSE TO 6 INCHES OF SNOW
WHICH IS BORDERLINE ADVISORY CRITERIA. MOUNT BAKER MAY GET THE
HIGHER AMOUNTS IN THIS PATTERN. PRECIPITATION WILL FALL AS JUST RAIN
IN THE LOWLANDS...CHANGING TO SHOWERS DURING THE AFTERNOON. ANY
BREAK IN PRECIPITATION WILL AGAIN BE SHORT LIVED AS A STRONG 180+ KT
JET ACROSS THE PACIFIC DRIVES WETTER STORMS TOWARD THE AREA BY
SATURDAY.  MERCER

.LONG TERM...NO UPDATES FROM PREVIOUS DISCUSSION...LOOKS LIKE A
SHORT BREAK IN THE WEATHER FRIDAY NIGHT BEFORE THE NEXT WETTER
SYSTEM ARRIVES OVER THE WEEKEND. THIS SYSTEM WAS CURRENTLY MOVING
ACROSS 150E THIS MORNING WITH A SUPPORTING 200 KT JET. THE PROGS ARE
STILL TRENDING A BIT DRIER WITH THIS SYSTEM GIVEN ITS MORE
PROGRESSIVE NATURE. EXPECT RAIN TO INCREASE ON SATURDAY WITH THE
WARM FRONT AND THE COLD FRONT MOVING ONSHORE SUNDAY NIGHT.

RIDGING ALOFT ALONG THE WEST COAST MEANS THE JET STREAM WILL BE AT
OUR LATITUDE WITH A WESTERLY COMPONENT INTO THE CASCADES AND
SHADOWING OFF THE OLYMPICS THIS WEEKEND. THE COAST AND MOUNTAINS
SHOULD GET THE BULK OF THE PRECIPITATION.

ANOTHER SHORT BREAK MONDAY BEFORE THE NEXT NOT AS WET SYSTEM ARRIVES
TUESDAY. THE PROGS CONTINUE TO SUGGEST A KONA LOW DEVELOPING BUT
THEY ARE INCONSISTENT IN ITS POSITION. THE FURTHER WEST USUALLY
RESULTS IN BUILDING AN UPPER RIDGE NEAR 150W OR 160W AND PRODUCING
NORTHERLY FLOW ALOFT INTO THE PACIFIC NW FOR A MUCH COOLER FLOW
PATTERN. FURTHER EAST WITH THE PATTERN AND THE PACIFIC NW GETS A
MILDER NORTHERLY FLOW ALOFT. STAY TUNED HERE. BUEHNER

&&

.HYDROLOGY...NO UPDATES FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH SATURDAY. MOIST WESTERLY FLOW WILL DEVELOP
SATURDAY NIGHT AND CONTINUE THROUGH SUNDAY NIGHT...WITH HEAVY
MOUNTAIN RAIN AMOUNTS POSSIBLE. GUIDANCE IS NOW SHOWING A BIT
LIGHTER AMOUNTS GIVEN THE MORE PROGRESSIVE NATURE OF THIS SYSTEM.
PRIMARY CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE
SKOKOMISH BUT ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE
STREAMS. BUEHNER

&&

.AVIATION...A STRETCHED OUT AND WEAKENING UPPER LEVEL TROUGH ALONG
THE COAST IS MOVING ONSHORE THIS MORNING AND WILL BE FOLLOWED BY
ANOTHER ONE...CURRENTLY ALONG 132W...TONIGHT. AT THE SURFACE...HIGH
PRES E OF THE CASCADES COMBINED WITH LOWER PRES OVER THE COASTAL
WATERS IS GIVING LIGHT OFFSHORE FLOW. THE AIR MASS IS MOIST AND
STABLE WITH LIGHT S TO SW FLOW ALOFT.

PACIFIC NW RADARS SHOW BANDS OF LIGHT RAIN EXTENDING SW FROM WESTERN
WASHINGTON INTO THE OREGON COASTAL WATERS. THIS MOISTURE IS MOVING
NE AHEAD OF THE INCOMING WEAKENING TROUGHS OFFSHORE. MOST
TERMINALS IN THE INTERIOR ARE SEEING VFR CEILINGS AND VISIBILITIES
DESPITE THE LIGHT RAIN AS A RESULT OF THE OFFSHORE PRES GRADIENTS.
THE EXCEPTIONS ARE AT KCLM WHERE PRECIPITATION AND FLOW MOVING ONTO
THE NORTH SLOPES OF THE OLYMPICS IS PRODUCING A LOWER STRATUS DECK
AND AROUND KOLM WHERE PRECIPITATION IN THE MORE TRAPPED SOUTHWEST
INTERIOR IS PRODUCING LOW IFR STRATUS AND VIS 3-5SM BR.

THE OFFSHORE PRES GRADIENTS ARE EXPECTED TO SLOWLY RELAX THROUGH
TONIGHT AS THE STRETCHING AND DYING TROUGHS OFFSHORE MOVE INTO THE
AREA. THIS WILL RESULT IN GENERALLY DETERIORATING CEILINGS AND
POORER VISIBILITIES AS WE MOVE INTO THE TONIGHT AND THU MORNING
PERIODS. EXPECT AREAS OF IFR CONDITIONS 06Z-18Z THU AT MANY OF THE
TERMINALS IN WESTERN WASHINGTON. ALBRECHT

KSEA...EXPECT CIGS AROUND 040 THROUGH THIS EVENING WITH PERIODS OF
LIGHT RAIN. CEILINGS WILL FALL TO 008-012 AFTER 05Z THIS EVENING AND
CONTINUE UNTIL 18Z. EXPECT VIS TO GENERALLY REMAIN ABOVE 5SM IN OCNL
-RA. EAST WIND AROUND 5 KT BECOMING SE TONIGHT. ALBRECHT

&&

.MARINE...WEAK TROUGHS OF LOW PRES...ONE OVER THE COASTAL WATERS AND
ANOTHER OVER THE OFFSHORE WATERS...WILL STRETCH OUT AND DIE AS THEY
MOVE INTO THE WATERS THIS AFTERNOON THROUGH TONIGHT. EXPECT LIGHT
OFFSHORE FLOW. WITH SEAS OVER THE COASTAL WATERS REMAINING AROUND 10
FT...THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED INTO
THE NEARSHORE COASTAL WATERS. SEAS WILL SUBSIDE LATE THIS AFTERNOON
AND TONIGHT.

A STRONG PACIFIC FRONT ASSOCIATED WITH A 960 MB LOW CENTERED NEAR
49N 159W WILL APPROACH THE OFFSHORE WATERS ON THU...THEN MOVE INLAND
THU NIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS LATER THU AFTERNOON THRU THU NIGHT AHEAD OF AND WITH
THE FRONT. A GALE WATCH IS IN EFFECT FOR THE COASTAL WATERS FOR THU
AFTERNOON AND NIGHT. THESE WILL LIKELY BE UPGRADED TO WARNINGS THIS
AFTERNOON.

THE FETCH AREA TO THE SOUTH OF THE LOW NEAR 49N 159W IS MOVING WITH
THE WAVE FIELD IT IS PRODUCING. THE WAVEWATCH MODEL CONTINUES TO
FORECAST SEAS 40-45 FT AROUND 47N 150W BY LATE TONIGHT. THESE WAVES
ARE EXPECTED TO DECAY INTO AN ENERGETIC 20-22 FT AT 18-20 SEC SWELL
ON THE WASHINGTON COAST LATE FRI AFTERNOON AND FRI NIGHT. AS IT
TURNS OUT...TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FT ABOVE
NORMAL AND HIGH TIDE OCCURS EARLY SAT MORNING. IF SWELL REMAINS HIGH
INTO SAT MORNING...SOME COASTAL FLOODING IS POSSIBLE ALONG PORTIONS
OF THE COASTAL WATERS. IT IS TOO EARLY TO TELL AT THIS POINT AND TOO
EARLY TO ISSUE ANY COASTAL FLOOD WATCHES...BUT INTERESTS ON THE
COAST ARE URGED TO KEEP UP WITH LATEST FORECASTS.

ANOTHER STRONG WARM FRONT WILL ARRIVE ON SAT AND WILL LIKELY RESULT
IN A PERIOD OF GALE FORCE WINDS OVER THE COASTAL WATERS...THE NORTH
INLAND WATERS...AND THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA.
ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY TODAY FOR HAZARDOUS SEAS COASTAL
      WATERS.
     SMALL CRAFT ADVISORY TODAY FOR ROUGH GRAYS HARBOR BAR.
     GALE WATCH MIDDAY THURSDAY THROUGH LATE THURSDAY NIGHT FOR
      THE COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML











000
FXUS66 KSEW 171713
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST WED DEC 17 2014

.SYNOPSIS...A WEAK PACIFIC WEATHER SYSTEM WILL BRING SOME AREAS OF
LIGHT RAIN TO WESTERN WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER
PACIFIC FRONTAL SYSTEM IS EXPECTED TO MOVE ASHORE THURSDAY NIGHT
WITH MORE SIGNIFICANT RAIN. ANOTHER WET WEATHER SYSTEM IS FORECAST
FOR THIS WEEKEND WITH HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN
THE MOUNTAINS.

&&

.SHORT TERM...MODELS ARE NOT HANDLING THE NRN STREAM PORTION OF THE
SPLIT TROUGH AFFECTING WRN WA ALL THAT WELL. THE ELONGATED 500 MB
TROUGH AXIS IS OFFSHORE JUST INSIDE 130 W AND THERE IS STILL SOME
SURFACE STRUCTURE LEFT ACCORDING THE HRRR WHICH MOST MODELS DO NOT
SHOW. THE HRRR FROM YESTERDAY AFTERNOON IS THE WINNER WHICH WAS
SHOWING SLY FLOW ENTRAINING SOME MOISTURE FROM THE SRN STREAM SYSTEM
INTO WRN WA EARLY THIS MORNING. RADAR NOW SHOWS LIGHT RAIN AROUND
MUCH OF WRN WA INCLUDING PUGET SOUND. SOME MODELS LIKE THE GFS40
WERE MOSTLY DRY AND STILL SHOW ONLY LIGHT QPF FIELDS W OF THE SOUND
AND ACROSS THE FAR N AND CASCADES. THE HRRR DOES DRY OUT THE
INTERIOR BY LATE MORNING BEFORE SPREADING SOME LIGHT RAIN BACK INTO
THE AREA EARLY THIS EVENING LIKE THE NAM12 SHOWS. THIS TIMING IS
QUESTIONABLE GIVEN THE BRIGHT CLOUDS ON IR IMAGERY APPROACHING THE
COAST COUPLED WITH THE LANGLEY HILL RADAR SHOWING MORE RAIN BANDS
ALONG THE COAST LIFTING NE. WILL MAINTAIN THE CURRENT LIKELY POPS
FOR TODAY AND TONIGHT.

THE 500 MB TROUGH AXIS FINALLY SHIFTS E OF THE AREA BY 12Z THURSDAY
MORNING. WITH LIGHT FLOW AND A SHORT WAVE RIDGE TRAVERSING THE
AREA...EXPECT LOW CLOUDS AND MAYBE SOME FOG AROUND THE AREA. THIS
WILL BREAK UP BY MIDDAY AS THE NEXT STRONGER FRONT APPROACHES
INCREASING THE FLOW OUT AHEAD OF IT. TIMING IS STILL TRICKY WITH THE
06Z GFS BRINGING RAIN AS FAR INLAND AS THE WRN PORTION OF PUGET
SOUND BY LATE THURSDAY AFTERNOON. THE NAM12/ECMWF ARE SIMILAR BUT
THE CANADIAN IS STILL RUNNING A FEW HOURS FASTER WITH RAIN
OVERSPREADING WRN WA EARLIER IN THE AFTERNOON. WILL LEAVE POPS
UNCHANGED FOR NOW BUT MAY CONSIDER REMOVING SOME OF THE INTERIOR
POPS FOR A DRY PERIOD THURSDAY MORNING. THIS WOULD PROBABLY RESULT
IN MORE FOG AROUND THE AREA.

THE WARM FRONT MOVES THROUGH QUICKLY WITH COLDER AIR ARRIVING WITH
THE MAIN FRONTAL BAND SLATED FOR THURSDAY NIGHT. THIS SYSTEM APPEARS
TO SPLIT LESS THAN PREVIOUS FRONTS AND THE SE GRADIENTS ARE TIGHT
OVER THE AREA SO EXPECT LOCALLY WINDY CONDITIONS NORTH OF PUGET
SOUND AND ALONG THE COAST. SNOW LEVELS WILL FALL FROM NEAR 5000 FEET
TO 3000 TO 3500 FEET BY LATER THURSDAY NIGHT AND FRIDAY MORNING.
THERE IS A 6 HOUR WINDOW OF STRONGER FLOW ALONG AND BEHIND THE FRONT
WHICH COULD SQUEEZE OUT SEVERAL INCHES OF SNOW EVEN DOWN TO SOME OF
THE PASSES. SKI RESORTS COULD POSSIBLY GET CLOSE TO 6 INCHES OF SNOW
WHICH IS BORDERLINE ADVISORY CRITERIA. MOUNT BAKER MAY GET THE
HIGHER AMOUNTS IN THIS PATTERN. PRECIPITATION WILL FALL AS JUST RAIN
IN THE LOWLANDS...CHANGING TO SHOWERS DURING THE AFTERNOON. ANY
BREAK IN PRECIPITATION WILL AGAIN BE SHORT LIVED AS A STRONG 180+ KT
JET ACROSS THE PACIFIC DRIVES WETTER STORMS TOWARD THE AREA BY
SATURDAY.  MERCER

.LONG TERM...NO UPDATES FROM PREVIOUS DISCUSSION...LOOKS LIKE A
SHORT BREAK IN THE WEATHER FRIDAY NIGHT BEFORE THE NEXT WETTER
SYSTEM ARRIVES OVER THE WEEKEND. THIS SYSTEM WAS CURRENTLY MOVING
ACROSS 150E THIS MORNING WITH A SUPPORTING 200 KT JET. THE PROGS ARE
STILL TRENDING A BIT DRIER WITH THIS SYSTEM GIVEN ITS MORE
PROGRESSIVE NATURE. EXPECT RAIN TO INCREASE ON SATURDAY WITH THE
WARM FRONT AND THE COLD FRONT MOVING ONSHORE SUNDAY NIGHT.

RIDGING ALOFT ALONG THE WEST COAST MEANS THE JET STREAM WILL BE AT
OUR LATITUDE WITH A WESTERLY COMPONENT INTO THE CASCADES AND
SHADOWING OFF THE OLYMPICS THIS WEEKEND. THE COAST AND MOUNTAINS
SHOULD GET THE BULK OF THE PRECIPITATION.

ANOTHER SHORT BREAK MONDAY BEFORE THE NEXT NOT AS WET SYSTEM ARRIVES
TUESDAY. THE PROGS CONTINUE TO SUGGEST A KONA LOW DEVELOPING BUT
THEY ARE INCONSISTENT IN ITS POSITION. THE FURTHER WEST USUALLY
RESULTS IN BUILDING AN UPPER RIDGE NEAR 150W OR 160W AND PRODUCING
NORTHERLY FLOW ALOFT INTO THE PACIFIC NW FOR A MUCH COOLER FLOW
PATTERN. FURTHER EAST WITH THE PATTERN AND THE PACIFIC NW GETS A
MILDER NORTHERLY FLOW ALOFT. STAY TUNED HERE. BUEHNER

&&

.HYDROLOGY...NO UPDATES FROM PREVIOUS DISCUSSION...RIVER FLOODING IS
NOT EXPECTED THROUGH SATURDAY. MOIST WESTERLY FLOW WILL DEVELOP
SATURDAY NIGHT AND CONTINUE THROUGH SUNDAY NIGHT...WITH HEAVY
MOUNTAIN RAIN AMOUNTS POSSIBLE. GUIDANCE IS NOW SHOWING A BIT
LIGHTER AMOUNTS GIVEN THE MORE PROGRESSIVE NATURE OF THIS SYSTEM.
PRIMARY CONCERN FOR ANY RIVER RISING ABOVE FLOOD STAGE IS THE
SKOKOMISH BUT ALSO NEED TO KEEP AN EYE ON OTHER CASCADE FLOOD PRONE
STREAMS. BUEHNER

&&

.AVIATION...A STRETCHED OUT AND WEAKENING UPPER LEVEL TROUGH ALONG
THE COAST IS MOVING ONSHORE THIS MORNING AND WILL BE FOLLOWED BY
ANOTHER ONE...CURRENTLY ALONG 132W...TONIGHT. AT THE SURFACE...HIGH
PRES E OF THE CASCADES COMBINED WITH LOWER PRES OVER THE COASTAL
WATERS IS GIVING LIGHT OFFSHORE FLOW. THE AIR MASS IS MOIST AND
STABLE WITH LIGHT S TO SW FLOW ALOFT.

PACIFIC NW RADARS SHOW BANDS OF LIGHT RAIN EXTENDING SW FROM WESTERN
WASHINGTON INTO THE OREGON COASTAL WATERS. THIS MOISTURE IS MOVING
NE AHEAD OF THE INCOMING WEAKENING TROUGHS OFFSHORE. MOST
TERMINALS IN THE INTERIOR ARE SEEING VFR CEILINGS AND VISIBILITIES
DESPITE THE LIGHT RAIN AS A RESULT OF THE OFFSHORE PRES GRADIENTS.
THE EXCEPTIONS ARE AT KCLM WHERE PRECIPITATION AND FLOW MOVING ONTO
THE NORTH SLOPES OF THE OLYMPICS IS PRODUCING A LOWER STRATUS DECK
AND AROUND KOLM WHERE PRECIPITATION IN THE MORE TRAPPED SOUTHWEST
INTERIOR IS PRODUCING LOW IFR STRATUS AND VIS 3-5SM BR.

THE OFFSHORE PRES GRADIENTS ARE EXPECTED TO SLOWLY RELAX THROUGH
TONIGHT AS THE STRETCHING AND DYING TROUGHS OFFSHORE MOVE INTO THE
AREA. THIS WILL RESULT IN GENERALLY DETERIORATING CEILINGS AND
POORER VISIBILITIES AS WE MOVE INTO THE TONIGHT AND THU MORNING
PERIODS. EXPECT AREAS OF IFR CONDITIONS 06Z-18Z THU AT MANY OF THE
TERMINALS IN WESTERN WASHINGTON. ALBRECHT

KSEA...EXPECT CIGS AROUND 040 THROUGH THIS EVENING WITH PERIODS OF
LIGHT RAIN. CEILINGS WILL FALL TO 008-012 AFTER 05Z THIS EVENING AND
CONTINUE UNTIL 18Z. EXPECT VIS TO GENERALLY REMAIN ABOVE 5SM IN OCNL
-RA. EAST WIND AROUND 5 KT BECOMING SE TONIGHT. ALBRECHT

&&

.MARINE...WEAK TROUGHS OF LOW PRES...ONE OVER THE COASTAL WATERS AND
ANOTHER OVER THE OFFSHORE WATERS...WILL STRETCH OUT AND DIE AS THEY
MOVE INTO THE WATERS THIS AFTERNOON THROUGH TONIGHT. EXPECT LIGHT
OFFSHORE FLOW. WITH SEAS OVER THE COASTAL WATERS REMAINING AROUND 10
FT...THE SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS WAS EXTENDED INTO
THE NEARSHORE COASTAL WATERS. SEAS WILL SUBSIDE LATE THIS AFTERNOON
AND TONIGHT.

A STRONG PACIFIC FRONT ASSOCIATED WITH A 960 MB LOW CENTERED NEAR
49N 159W WILL APPROACH THE OFFSHORE WATERS ON THU...THEN MOVE INLAND
THU NIGHT. A PERIOD OF GALE FORCE WINDS CAN BE EXPECTED OVER THE
COASTAL WATERS LATER THU AFTERNOON THRU THU NIGHT AHEAD OF AND WITH
THE FRONT. A GALE WATCH IS IN EFFECT FOR THE COASTAL WATERS FOR THU
AFTERNOON AND NIGHT. THESE WILL LIKELY BE UPGRADED TO WARNINGS THIS
AFTERNOON.

THE FETCH AREA TO THE SOUTH OF THE LOW NEAR 49N 159W IS MOVING WITH
THE WAVE FIELD IT IS PRODUCING. THE WAVEWATCH MODEL CONTINUES TO
FORECAST SEAS 40-45 FT AROUND 47N 150W BY LATE TONIGHT. THESE WAVES
ARE EXPECTED TO DECAY INTO AN ENERGETIC 20-22 FT AT 18-20 SEC SWELL
ON THE WASHINGTON COAST LATE FRI AFTERNOON AND FRI NIGHT. AS IT
TURNS OUT...TIDAL ANOMALIES ALONG THE COAST ARE JUST OVER 1 FT ABOVE
NORMAL AND HIGH TIDE OCCURS EARLY SAT MORNING. IF SWELL REMAINS HIGH
INTO SAT MORNING...SOME COASTAL FLOODING IS POSSIBLE ALONG PORTIONS
OF THE COASTAL WATERS. IT IS TOO EARLY TO TELL AT THIS POINT AND TOO
EARLY TO ISSUE ANY COASTAL FLOOD WATCHES...BUT INTERESTS ON THE
COAST ARE URGED TO KEEP UP WITH LATEST FORECASTS.

ANOTHER STRONG WARM FRONT WILL ARRIVE ON SAT AND WILL LIKELY RESULT
IN A PERIOD OF GALE FORCE WINDS OVER THE COASTAL WATERS...THE NORTH
INLAND WATERS...AND THE ENTRANCES TO THE STRAIT OF JUAN DE FUCA.
ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY TODAY FOR HAZARDOUS SEAS COASTAL
      WATERS.
     SMALL CRAFT ADVISORY TODAY FOR ROUGH GRAYS HARBOR BAR.
     GALE WATCH MIDDAY THURSDAY THROUGH LATE THURSDAY NIGHT FOR
      THE COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML











000
FXUS66 KOTX 171603
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
803 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.



&&

.DISCUSSION...
Quick update to increase pops and snow amounts for Wenatchee and
Waterville Plateau area as radar likly missing the stronger
returns as snow falls from lower cloud deck in that area. The wave
is weak and moving northeast. /Pelatti

&&

.AVIATION...
12Z TAFS: A few light flurries will be possible north of Spokane
through 15z...and snow will be on the increase near the crest of
the Cascades this morning as well. A northeast surface gradient
has scoured out the fog for all the TAF sites except for KEAT.
The stratus has also lifted into a mid level deck with VFR
conditions. KEAT is still in the fog and stratus with
MVFR cigs/vsby. The next weather disturbance will push across the
region later this morning. Light rain is expected at KEAT and
KMWH by mid morning. Behind the precipitation fog/stratus is once
again expected for KEAT/KMWH after 03z with MVFR/IFR cigs/vsby.
Precipitation...as mainly rain will hold for the eastern TAF
sites until late this afternoon and linger into the evening. MVFR
cigs/vsby expected with the rain. Tobin


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 / 100  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 171603
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
803 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.



&&

.DISCUSSION...
Quick update to increase pops and snow amounts for Wenatchee and
Waterville Plateau area as radar likly missing the stronger
returns as snow falls from lower cloud deck in that area. The wave
is weak and moving northeast. /Pelatti

&&

.AVIATION...
12Z TAFS: A few light flurries will be possible north of Spokane
through 15z...and snow will be on the increase near the crest of
the Cascades this morning as well. A northeast surface gradient
has scoured out the fog for all the TAF sites except for KEAT.
The stratus has also lifted into a mid level deck with VFR
conditions. KEAT is still in the fog and stratus with
MVFR cigs/vsby. The next weather disturbance will push across the
region later this morning. Light rain is expected at KEAT and
KMWH by mid morning. Behind the precipitation fog/stratus is once
again expected for KEAT/KMWH after 03z with MVFR/IFR cigs/vsby.
Precipitation...as mainly rain will hold for the eastern TAF
sites until late this afternoon and linger into the evening. MVFR
cigs/vsby expected with the rain. Tobin


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 / 100  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 171156
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
353 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Today through Thursday night...The region will continue to be
under the influence of a split and ragged upper level trough
today and tonight. Again a couple of weak waves will move through
the forecast area and result in periods of light precipitation.
Cooler air banked up against the Cascades continues to make snow
level forecast a challenge. The 00z guidance came in with wet bulb
temperatures down around 30F when in fact the wet bulbs are in the
low to mid 30s. I most likely kept snow levels a little to low
across the areas for this morning, otherwise snow levels are
anywhere from 2500 to around 4000 feet across the area. So any
precipitation will be valley rain...possibly mixed with a little
snow for the Methow and up near Ardnevoir and mountain snow.
Precipitation amounts will remain light with a few hundredths in
the basin and lower valleys and possibly up to a tenth in the
mountains. Snow accumulations even for the mountains will only be
an inch or two.

Precipitation chances will then be on the decrease from the west
for the remainder of the night and Thursday as a short lived ridge
of high pressure builds into the region. Some pops were kept in
the orographically favored Panhandle mountains, but again
accumulations should remain light with light snow above 3500 feet
for the Panhandle. Fog and stratus will likely develop through
the night and Thursday morning with a saturated boundary layer and
light south-southwest winds.

The next system will move towards the region Thursday night and
increase Pacific moisture. Snow levels for the valleys near the
Cascades will again be problematic. I don`t see any freezing rain
at this time but precipitation probably as a snow or snow/rain mix
for those valleys and snow above 3000-3500 feet. Some of the
higher locations in the Cascades could see 3-5 inches of fresh
snow by early Friday morning. Tobin

Friday and Friday night...The next in a series of Pacific weather
systems pushes across the Inland Northwest on Friday with a warm
front followed closely by an occluded front Friday evening. This
one looks to be a little stronger and a little warmer.
Precipitation type will be tricky with light snow in the morning,
turning to valley rain and mountain snow by afternoon. There looks
to be the potential for up to an inch in the northern valleys,
while the northern mountains could see 1-3 inches. Drying occurs
behind the front Friday night with a brief break in the
precipitation and light winds.

Saturday through Sunday night...This still looks to be a wettest
period as an atmospheric river takes aim on the Pacific NW. The
GFS and ECMWF show agreement of moderate isentropic lift spreading
across the region Saturday morning with a stream of plentiful
moisture for most of the weekend. Again precipitation type will be
tricky, initially with valley snow possible in the valley northern
valleys especially in the Cascade valleys. Warming increases
Saturday night into Sunday, making it a mainly rain/high mountain
snow event by Sunday afternoon. The 850mb 0C line pushes to the
Canadian border on Sunday while temps of +5C to +7C poke into the
Columbia Basin. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. Moderate to heavy rainfall
is possible with juicy QPF amounts of 0.25" to 0.40" during a 24
hour period Saturday night into Sunday. Winds will increase by
Sunday evening with speeds 25-35 kts across the Columbia Basin.
Could even see some gusty mountain winds across the Cascades by
Sunday night. POPs and QPF amounts have been raised and winds
bumped for this period.

Monday through Tuesday...A cold front slides through the region
Monday allowing the atmospheric river to sag southward and cooler
drier air to filter in from the north. The bulk of the precipitation
will be found in the Cascades and Panhandle mountains through
Monday morning and then gradually taper off. Drier conditions and
clearing will allow temperatures to cool Monday night. This will
set the stage for the next weather system. Under the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. A warm front will spread light precipitation across
eastern Washington by Tuesday. Based on low level temperatures,
there is good chance that the precipitation type will start off as
snow for most areas. /rfox.

&&

.AVIATION...
12Z TAFS: A few light flurries will be possible north of Spokane
through 15z...and snow will be on the increase near the crest of
the Cascades this morning as well. A northeast surface gradient
has scoured out the fog for all the TAF sites except for KEAT.
The stratus has also lifted into a mid level deck with VFR
conditions. KEAT is still in the fog and stratus with
MVFR cigs/vsby. The next weather disturbance will push across the
region later this morning. Light rain is expected at KEAT and
KMWH by mid morning. Behind the precipitation fog/stratus is once
again expected for KEAT/KMWH after 03z with MVFR/IFR cigs/vsby.
Precipitation...as mainly rain will hold for the eastern TAF
sites until late this afternoon and linger into the evening. MVFR
cigs/vsby expected with the rain. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 /  50  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 171156
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
353 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Today through Thursday night...The region will continue to be
under the influence of a split and ragged upper level trough
today and tonight. Again a couple of weak waves will move through
the forecast area and result in periods of light precipitation.
Cooler air banked up against the Cascades continues to make snow
level forecast a challenge. The 00z guidance came in with wet bulb
temperatures down around 30F when in fact the wet bulbs are in the
low to mid 30s. I most likely kept snow levels a little to low
across the areas for this morning, otherwise snow levels are
anywhere from 2500 to around 4000 feet across the area. So any
precipitation will be valley rain...possibly mixed with a little
snow for the Methow and up near Ardnevoir and mountain snow.
Precipitation amounts will remain light with a few hundredths in
the basin and lower valleys and possibly up to a tenth in the
mountains. Snow accumulations even for the mountains will only be
an inch or two.

Precipitation chances will then be on the decrease from the west
for the remainder of the night and Thursday as a short lived ridge
of high pressure builds into the region. Some pops were kept in
the orographically favored Panhandle mountains, but again
accumulations should remain light with light snow above 3500 feet
for the Panhandle. Fog and stratus will likely develop through
the night and Thursday morning with a saturated boundary layer and
light south-southwest winds.

The next system will move towards the region Thursday night and
increase Pacific moisture. Snow levels for the valleys near the
Cascades will again be problematic. I don`t see any freezing rain
at this time but precipitation probably as a snow or snow/rain mix
for those valleys and snow above 3000-3500 feet. Some of the
higher locations in the Cascades could see 3-5 inches of fresh
snow by early Friday morning. Tobin

Friday and Friday night...The next in a series of Pacific weather
systems pushes across the Inland Northwest on Friday with a warm
front followed closely by an occluded front Friday evening. This
one looks to be a little stronger and a little warmer.
Precipitation type will be tricky with light snow in the morning,
turning to valley rain and mountain snow by afternoon. There looks
to be the potential for up to an inch in the northern valleys,
while the northern mountains could see 1-3 inches. Drying occurs
behind the front Friday night with a brief break in the
precipitation and light winds.

Saturday through Sunday night...This still looks to be a wettest
period as an atmospheric river takes aim on the Pacific NW. The
GFS and ECMWF show agreement of moderate isentropic lift spreading
across the region Saturday morning with a stream of plentiful
moisture for most of the weekend. Again precipitation type will be
tricky, initially with valley snow possible in the valley northern
valleys especially in the Cascade valleys. Warming increases
Saturday night into Sunday, making it a mainly rain/high mountain
snow event by Sunday afternoon. The 850mb 0C line pushes to the
Canadian border on Sunday while temps of +5C to +7C poke into the
Columbia Basin. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. Moderate to heavy rainfall
is possible with juicy QPF amounts of 0.25" to 0.40" during a 24
hour period Saturday night into Sunday. Winds will increase by
Sunday evening with speeds 25-35 kts across the Columbia Basin.
Could even see some gusty mountain winds across the Cascades by
Sunday night. POPs and QPF amounts have been raised and winds
bumped for this period.

Monday through Tuesday...A cold front slides through the region
Monday allowing the atmospheric river to sag southward and cooler
drier air to filter in from the north. The bulk of the precipitation
will be found in the Cascades and Panhandle mountains through
Monday morning and then gradually taper off. Drier conditions and
clearing will allow temperatures to cool Monday night. This will
set the stage for the next weather system. Under the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. A warm front will spread light precipitation across
eastern Washington by Tuesday. Based on low level temperatures,
there is good chance that the precipitation type will start off as
snow for most areas. /rfox.

&&

.AVIATION...
12Z TAFS: A few light flurries will be possible north of Spokane
through 15z...and snow will be on the increase near the crest of
the Cascades this morning as well. A northeast surface gradient
has scoured out the fog for all the TAF sites except for KEAT.
The stratus has also lifted into a mid level deck with VFR
conditions. KEAT is still in the fog and stratus with
MVFR cigs/vsby. The next weather disturbance will push across the
region later this morning. Light rain is expected at KEAT and
KMWH by mid morning. Behind the precipitation fog/stratus is once
again expected for KEAT/KMWH after 03z with MVFR/IFR cigs/vsby.
Precipitation...as mainly rain will hold for the eastern TAF
sites until late this afternoon and linger into the evening. MVFR
cigs/vsby expected with the rain. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 /  50  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 171156
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
353 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Today through Thursday night...The region will continue to be
under the influence of a split and ragged upper level trough
today and tonight. Again a couple of weak waves will move through
the forecast area and result in periods of light precipitation.
Cooler air banked up against the Cascades continues to make snow
level forecast a challenge. The 00z guidance came in with wet bulb
temperatures down around 30F when in fact the wet bulbs are in the
low to mid 30s. I most likely kept snow levels a little to low
across the areas for this morning, otherwise snow levels are
anywhere from 2500 to around 4000 feet across the area. So any
precipitation will be valley rain...possibly mixed with a little
snow for the Methow and up near Ardnevoir and mountain snow.
Precipitation amounts will remain light with a few hundredths in
the basin and lower valleys and possibly up to a tenth in the
mountains. Snow accumulations even for the mountains will only be
an inch or two.

Precipitation chances will then be on the decrease from the west
for the remainder of the night and Thursday as a short lived ridge
of high pressure builds into the region. Some pops were kept in
the orographically favored Panhandle mountains, but again
accumulations should remain light with light snow above 3500 feet
for the Panhandle. Fog and stratus will likely develop through
the night and Thursday morning with a saturated boundary layer and
light south-southwest winds.

The next system will move towards the region Thursday night and
increase Pacific moisture. Snow levels for the valleys near the
Cascades will again be problematic. I don`t see any freezing rain
at this time but precipitation probably as a snow or snow/rain mix
for those valleys and snow above 3000-3500 feet. Some of the
higher locations in the Cascades could see 3-5 inches of fresh
snow by early Friday morning. Tobin

Friday and Friday night...The next in a series of Pacific weather
systems pushes across the Inland Northwest on Friday with a warm
front followed closely by an occluded front Friday evening. This
one looks to be a little stronger and a little warmer.
Precipitation type will be tricky with light snow in the morning,
turning to valley rain and mountain snow by afternoon. There looks
to be the potential for up to an inch in the northern valleys,
while the northern mountains could see 1-3 inches. Drying occurs
behind the front Friday night with a brief break in the
precipitation and light winds.

Saturday through Sunday night...This still looks to be a wettest
period as an atmospheric river takes aim on the Pacific NW. The
GFS and ECMWF show agreement of moderate isentropic lift spreading
across the region Saturday morning with a stream of plentiful
moisture for most of the weekend. Again precipitation type will be
tricky, initially with valley snow possible in the valley northern
valleys especially in the Cascade valleys. Warming increases
Saturday night into Sunday, making it a mainly rain/high mountain
snow event by Sunday afternoon. The 850mb 0C line pushes to the
Canadian border on Sunday while temps of +5C to +7C poke into the
Columbia Basin. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. Moderate to heavy rainfall
is possible with juicy QPF amounts of 0.25" to 0.40" during a 24
hour period Saturday night into Sunday. Winds will increase by
Sunday evening with speeds 25-35 kts across the Columbia Basin.
Could even see some gusty mountain winds across the Cascades by
Sunday night. POPs and QPF amounts have been raised and winds
bumped for this period.

Monday through Tuesday...A cold front slides through the region
Monday allowing the atmospheric river to sag southward and cooler
drier air to filter in from the north. The bulk of the precipitation
will be found in the Cascades and Panhandle mountains through
Monday morning and then gradually taper off. Drier conditions and
clearing will allow temperatures to cool Monday night. This will
set the stage for the next weather system. Under the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. A warm front will spread light precipitation across
eastern Washington by Tuesday. Based on low level temperatures,
there is good chance that the precipitation type will start off as
snow for most areas. /rfox.

&&

.AVIATION...
12Z TAFS: A few light flurries will be possible north of Spokane
through 15z...and snow will be on the increase near the crest of
the Cascades this morning as well. A northeast surface gradient
has scoured out the fog for all the TAF sites except for KEAT.
The stratus has also lifted into a mid level deck with VFR
conditions. KEAT is still in the fog and stratus with
MVFR cigs/vsby. The next weather disturbance will push across the
region later this morning. Light rain is expected at KEAT and
KMWH by mid morning. Behind the precipitation fog/stratus is once
again expected for KEAT/KMWH after 03z with MVFR/IFR cigs/vsby.
Precipitation...as mainly rain will hold for the eastern TAF
sites until late this afternoon and linger into the evening. MVFR
cigs/vsby expected with the rain. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 /  50  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 171156
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
353 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Today through Thursday night...The region will continue to be
under the influence of a split and ragged upper level trough
today and tonight. Again a couple of weak waves will move through
the forecast area and result in periods of light precipitation.
Cooler air banked up against the Cascades continues to make snow
level forecast a challenge. The 00z guidance came in with wet bulb
temperatures down around 30F when in fact the wet bulbs are in the
low to mid 30s. I most likely kept snow levels a little to low
across the areas for this morning, otherwise snow levels are
anywhere from 2500 to around 4000 feet across the area. So any
precipitation will be valley rain...possibly mixed with a little
snow for the Methow and up near Ardnevoir and mountain snow.
Precipitation amounts will remain light with a few hundredths in
the basin and lower valleys and possibly up to a tenth in the
mountains. Snow accumulations even for the mountains will only be
an inch or two.

Precipitation chances will then be on the decrease from the west
for the remainder of the night and Thursday as a short lived ridge
of high pressure builds into the region. Some pops were kept in
the orographically favored Panhandle mountains, but again
accumulations should remain light with light snow above 3500 feet
for the Panhandle. Fog and stratus will likely develop through
the night and Thursday morning with a saturated boundary layer and
light south-southwest winds.

The next system will move towards the region Thursday night and
increase Pacific moisture. Snow levels for the valleys near the
Cascades will again be problematic. I don`t see any freezing rain
at this time but precipitation probably as a snow or snow/rain mix
for those valleys and snow above 3000-3500 feet. Some of the
higher locations in the Cascades could see 3-5 inches of fresh
snow by early Friday morning. Tobin

Friday and Friday night...The next in a series of Pacific weather
systems pushes across the Inland Northwest on Friday with a warm
front followed closely by an occluded front Friday evening. This
one looks to be a little stronger and a little warmer.
Precipitation type will be tricky with light snow in the morning,
turning to valley rain and mountain snow by afternoon. There looks
to be the potential for up to an inch in the northern valleys,
while the northern mountains could see 1-3 inches. Drying occurs
behind the front Friday night with a brief break in the
precipitation and light winds.

Saturday through Sunday night...This still looks to be a wettest
period as an atmospheric river takes aim on the Pacific NW. The
GFS and ECMWF show agreement of moderate isentropic lift spreading
across the region Saturday morning with a stream of plentiful
moisture for most of the weekend. Again precipitation type will be
tricky, initially with valley snow possible in the valley northern
valleys especially in the Cascade valleys. Warming increases
Saturday night into Sunday, making it a mainly rain/high mountain
snow event by Sunday afternoon. The 850mb 0C line pushes to the
Canadian border on Sunday while temps of +5C to +7C poke into the
Columbia Basin. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. Moderate to heavy rainfall
is possible with juicy QPF amounts of 0.25" to 0.40" during a 24
hour period Saturday night into Sunday. Winds will increase by
Sunday evening with speeds 25-35 kts across the Columbia Basin.
Could even see some gusty mountain winds across the Cascades by
Sunday night. POPs and QPF amounts have been raised and winds
bumped for this period.

Monday through Tuesday...A cold front slides through the region
Monday allowing the atmospheric river to sag southward and cooler
drier air to filter in from the north. The bulk of the precipitation
will be found in the Cascades and Panhandle mountains through
Monday morning and then gradually taper off. Drier conditions and
clearing will allow temperatures to cool Monday night. This will
set the stage for the next weather system. Under the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. A warm front will spread light precipitation across
eastern Washington by Tuesday. Based on low level temperatures,
there is good chance that the precipitation type will start off as
snow for most areas. /rfox.

&&

.AVIATION...
12Z TAFS: A few light flurries will be possible north of Spokane
through 15z...and snow will be on the increase near the crest of
the Cascades this morning as well. A northeast surface gradient
has scoured out the fog for all the TAF sites except for KEAT.
The stratus has also lifted into a mid level deck with VFR
conditions. KEAT is still in the fog and stratus with
MVFR cigs/vsby. The next weather disturbance will push across the
region later this morning. Light rain is expected at KEAT and
KMWH by mid morning. Behind the precipitation fog/stratus is once
again expected for KEAT/KMWH after 03z with MVFR/IFR cigs/vsby.
Precipitation...as mainly rain will hold for the eastern TAF
sites until late this afternoon and linger into the evening. MVFR
cigs/vsby expected with the rain. Tobin

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 /  50  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KSEW 171100
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST WED DEC 17 2014

.SYNOPSIS...A WEAK PACIFIC WEATHER SYSTEM WILL BRING SOME AREAS OF
LIGHT RAIN TO WESTERN WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER
PACIFIC FRONTAL SYSTEM IS EXPECTED TO MOVE ASHORE THURSDAY NIGHT
WITH MORE SIGNIFICANT RAIN. ANOTHER WET WEATHER SYSTEM IS FORECAST
FOR THIS WEEKEND WITH HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN
THE MOUNTAINS.

&&

.SHORT TERM...A NEGATIVE TILTED UPPER TROUGH WITH SPLIT FLOW IS JUST
OFF THE COAST EARLY THIS MORNING. THE PRIMARY FLOW ALOFT IS INTO
CALIFORNIA WHERE THE BULK OF THE PRECIP IS HEADED. A WEAKENING
SHORTWAVE WAS PRODUCING LIGHT RAIN ALONG THE COAST AND SOME OF THAT
SHOULD MOVE FURTHER INLAND LATER TODAY. RAIN AMOUNTS LIGHT THOUGH.

THE NEXT SHORTWAVE ON SATELITE IMAGERY WAS MOVING INSIDE 135W AGAIN
WITH THE BULK OF THE ENERGY HEADING TOWARD THE GOLDEN STATE. THE
REMAINING STRETCHED OUT PORTION AT OUR LATITUDE WILL LIKELY SPREAD
SOME ADDITIONAL LIGHT RAIN ONSHORE TONIGHT.

THE NEXT UPSTREAM AND STRONGER SHORTWAVE WAS NEAR 160W EARLY THIS
MORNING. THIS SYSTEM WAS PUMPING UP A SHORTWAVE RIDGE AHEAD OF IT
THAT PROGS AGREE WILL MOVE ONSHORE THURSDAY. THEN THE ASSOCIATED
FRONTAL SYSTEM SHOULD BEGIN TO SPREAD RAIN ONSHORE LATE THURSDAY
WITH THE COLD FRONT MOVING INLAND EARLY FRIDAY. BLUSTERY WINDS FOR
THE COAST AND NORTH INTERIOR WITH THIS SYSTEM. THE SHORTWAVE TROUGH
IS THEN FORECAST TO MOVE ASHORE FOR A BIT COOLER SHOWERY DAY FRIDAY.

FOR THE MOUNTAINS...THE LACK OF SNOW IS A CONCERN. THE WEATHER
SYSTEMS TODAY THROUGH FRIDAY SHOULD PRODUCE AT LEAST SOME SNOWFALL
THERE. EAST TO WEST GRADIENTS ACROSS THE CASCADES SHOULD TEND TO
KEEP THE SNOW LEVELS CLOSE TO THE PASSES UNTIL THE THURSDAY NIGHT
SYSTEM MOVES ONSHORE EARLY FRIDAY. BY THEN...THE FOLLOWING SHORTWAVE
TROUGH WILL BRING SOME COOLER UNSTABLE AIR FOR SNOW SHOWERS. NOT A
WHOLE LOT OF SNOW IN THE NEXT 3 DAYS...BUT BETTER THAN LAST WEEKS
MILD WET WEATHER. BUEHNER

.LONG TERM...LOOKS LIKE A SHORT BREAK IN THE WEATHER FRIDAY NIGHT
BEFORE THE NEXT WETTER SYSTEM ARRIVES OVER THE WEEKEND. THIS SYSTEM
WAS CURRENTLY MOVING ACROSS 150E THIS MORNING WITH A SUPPORTING 200
KT JET. THE PROGS ARE STILL TRENDING A BIT DRIER WITH THIS SYSTEM
GIVEN ITS MORE PROGRESSIVE NATURE. EXPECT RAIN TO INCREASE ON
SATURDAY WITH THE WARM FRONT AND THE COLD FRONT MOVING ONSHORE
SUNDAY NIGHT.

RIDGING ALOFT ALONG THE WEST COAST MEANS THE JET STREAM WILL BE AT
OUR LATITUDE WITH A WESTERLY COMPONENT INTO THE CASCADES AND
SHADOWING OFF THE OLYMPICS THIS WEEKEND. THE COAST AND MOUNTAINS
SHOULD GET THE BULK OF THE PRECIPITATION.

ANOTHER SHORT BREAK MONDAY BEFORE THE NEXT NOT AS WET SYSTEM ARRIVES
TUESDAY. THE PROGS CONTINUE TO SUGGEST A KONA LOW DEVELOPING BUT
THEY ARE INCONSISTENT IN ITS POSITION. THE FURTHER WEST USUALLY
RESULTS IN BUILDING AN UPPER RIDGE NEAR 150W OR 160W AND PRODUCING
NORTHERLY FLOW ALOFT INTO THE PACIFIC NW FOR A MUCH COOLER FLOW
PATTERN. FURTHER EAST WITH THE PATTERN AND THE PACIFIC NW GETS A
MILDER NORTHERLY FLOW ALOFT. STAY TUNED HERE. BUEHNER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
SUNDAY NIGHT...WITH HEAVY MOUNTAIN RAIN AMOUNTS POSSIBLE.
GUIDANCE IS NOW SHOWING A BIT LIGHTER AMOUNTS GIVEN THE MORE
PROGRESSIVE NATURE OF THIS SYSTEM. PRIMARY CONCERN FOR ANY RIVER
RISING ABOVE FLOOD STAGE IS THE SKOKOMISH BUT ALSO NEED TO KEEP AN
EYE ON OTHER CASCADE FLOOD PRONE STREAMS. BUEHNER

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL GIVE LIGHT SOUTHWEST FLOW
ALOFT OVER WESTERN WASHINGTON TODAY. LOW LEVEL OFFSHORE FLOW WILL
EASE AS A SURFACE TROUGH MOVES ONSHORE AND RIDGING EAST OF THE
CASCADES WEAKENS. THE AIR MASS WILL REMAIN MOIST AND STABLE WITH
AREAS OF VERY LIGHT PRECIPITATION MOVING THROUGH AT TIMES.

STRATUS OVER THE SOUTHWEST INTERIOR OVERNIGHT IS ERODING AS HIGHER
LEVEL MOISTURE ASSOCIATED WITH INCOMING TROUGH INCREASES. A FEW
POCKETS OF SURFACE VSBYS 3-5SM COULD PERSIST AROUND KOLM THROUGH
15Z. MAINLY VFR CEILINGS EXPECTED THIS MORNING...BUT MODELS INDICATE
THE LOW LEVELS WILL MOISTEN UP LATER TODAY WITH SOME HIGHER END MVFR
CEILINGS POSSIBLE MIDDAY INTO THE EVENING AS LIGHT PRECIP ASSOCIATED
WITH TROUGH MOVES INLAND.

KSEA...VFR CEILINGS EXPECTED THROUGH LATE MORNING...BUT MAY SEE SOME
TEMPO BKN-OVC030 WITH LIGHT RAIN 18Z-00Z. MVFR CEILINGS MAY STICK
AROUND TONIGHT WITH LIGHT SURFACE GRADIENTS AND MOIST AIR MASS IN
PLACE. EAST-SOUTHEAST WIND 5 TO 10 KNOTS...BECOMING LIGHT SOUTHERLY
TONIGHT.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES
CONTINUE FOR THE OUTER COASTAL WATERS WHERE SEAS REMAIN NEAR 10
FEET. FOR THE REMAINDER OF THE WATERS...A PERIOD OF QUIET WEATHER IS
FORECAST TODAY WITH A WEAK SURFACE TROUGH OVER THE REGION. A BETTER
ORGANIZED AND STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY.
A GALE WATCH FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY
NIGHT REMAINS IN EFFECT FOR THIS. ANOTHER FRONT ON SATURDAY COULD
PRODUCES GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY TODAY FOR HAZARDOUS SEAS OUTER COASTAL
     WATERS.
     SMALL CRAFT ADVISORY TODAY FOR ROUGH GRAYS HARBOR BAR.
     GALE WATCH THURSDAY MORNING THROUGH LATE THURSDAY NIGHT FOR THE
     COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








000
FXUS66 KSEW 171100
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PST WED DEC 17 2014

.SYNOPSIS...A WEAK PACIFIC WEATHER SYSTEM WILL BRING SOME AREAS OF
LIGHT RAIN TO WESTERN WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER
PACIFIC FRONTAL SYSTEM IS EXPECTED TO MOVE ASHORE THURSDAY NIGHT
WITH MORE SIGNIFICANT RAIN. ANOTHER WET WEATHER SYSTEM IS FORECAST
FOR THIS WEEKEND WITH HEAVIER RAIN AMOUNTS ALONG THE COAST AND IN
THE MOUNTAINS.

&&

.SHORT TERM...A NEGATIVE TILTED UPPER TROUGH WITH SPLIT FLOW IS JUST
OFF THE COAST EARLY THIS MORNING. THE PRIMARY FLOW ALOFT IS INTO
CALIFORNIA WHERE THE BULK OF THE PRECIP IS HEADED. A WEAKENING
SHORTWAVE WAS PRODUCING LIGHT RAIN ALONG THE COAST AND SOME OF THAT
SHOULD MOVE FURTHER INLAND LATER TODAY. RAIN AMOUNTS LIGHT THOUGH.

THE NEXT SHORTWAVE ON SATELITE IMAGERY WAS MOVING INSIDE 135W AGAIN
WITH THE BULK OF THE ENERGY HEADING TOWARD THE GOLDEN STATE. THE
REMAINING STRETCHED OUT PORTION AT OUR LATITUDE WILL LIKELY SPREAD
SOME ADDITIONAL LIGHT RAIN ONSHORE TONIGHT.

THE NEXT UPSTREAM AND STRONGER SHORTWAVE WAS NEAR 160W EARLY THIS
MORNING. THIS SYSTEM WAS PUMPING UP A SHORTWAVE RIDGE AHEAD OF IT
THAT PROGS AGREE WILL MOVE ONSHORE THURSDAY. THEN THE ASSOCIATED
FRONTAL SYSTEM SHOULD BEGIN TO SPREAD RAIN ONSHORE LATE THURSDAY
WITH THE COLD FRONT MOVING INLAND EARLY FRIDAY. BLUSTERY WINDS FOR
THE COAST AND NORTH INTERIOR WITH THIS SYSTEM. THE SHORTWAVE TROUGH
IS THEN FORECAST TO MOVE ASHORE FOR A BIT COOLER SHOWERY DAY FRIDAY.

FOR THE MOUNTAINS...THE LACK OF SNOW IS A CONCERN. THE WEATHER
SYSTEMS TODAY THROUGH FRIDAY SHOULD PRODUCE AT LEAST SOME SNOWFALL
THERE. EAST TO WEST GRADIENTS ACROSS THE CASCADES SHOULD TEND TO
KEEP THE SNOW LEVELS CLOSE TO THE PASSES UNTIL THE THURSDAY NIGHT
SYSTEM MOVES ONSHORE EARLY FRIDAY. BY THEN...THE FOLLOWING SHORTWAVE
TROUGH WILL BRING SOME COOLER UNSTABLE AIR FOR SNOW SHOWERS. NOT A
WHOLE LOT OF SNOW IN THE NEXT 3 DAYS...BUT BETTER THAN LAST WEEKS
MILD WET WEATHER. BUEHNER

.LONG TERM...LOOKS LIKE A SHORT BREAK IN THE WEATHER FRIDAY NIGHT
BEFORE THE NEXT WETTER SYSTEM ARRIVES OVER THE WEEKEND. THIS SYSTEM
WAS CURRENTLY MOVING ACROSS 150E THIS MORNING WITH A SUPPORTING 200
KT JET. THE PROGS ARE STILL TRENDING A BIT DRIER WITH THIS SYSTEM
GIVEN ITS MORE PROGRESSIVE NATURE. EXPECT RAIN TO INCREASE ON
SATURDAY WITH THE WARM FRONT AND THE COLD FRONT MOVING ONSHORE
SUNDAY NIGHT.

RIDGING ALOFT ALONG THE WEST COAST MEANS THE JET STREAM WILL BE AT
OUR LATITUDE WITH A WESTERLY COMPONENT INTO THE CASCADES AND
SHADOWING OFF THE OLYMPICS THIS WEEKEND. THE COAST AND MOUNTAINS
SHOULD GET THE BULK OF THE PRECIPITATION.

ANOTHER SHORT BREAK MONDAY BEFORE THE NEXT NOT AS WET SYSTEM ARRIVES
TUESDAY. THE PROGS CONTINUE TO SUGGEST A KONA LOW DEVELOPING BUT
THEY ARE INCONSISTENT IN ITS POSITION. THE FURTHER WEST USUALLY
RESULTS IN BUILDING AN UPPER RIDGE NEAR 150W OR 160W AND PRODUCING
NORTHERLY FLOW ALOFT INTO THE PACIFIC NW FOR A MUCH COOLER FLOW
PATTERN. FURTHER EAST WITH THE PATTERN AND THE PACIFIC NW GETS A
MILDER NORTHERLY FLOW ALOFT. STAY TUNED HERE. BUEHNER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
SUNDAY NIGHT...WITH HEAVY MOUNTAIN RAIN AMOUNTS POSSIBLE.
GUIDANCE IS NOW SHOWING A BIT LIGHTER AMOUNTS GIVEN THE MORE
PROGRESSIVE NATURE OF THIS SYSTEM. PRIMARY CONCERN FOR ANY RIVER
RISING ABOVE FLOOD STAGE IS THE SKOKOMISH BUT ALSO NEED TO KEEP AN
EYE ON OTHER CASCADE FLOOD PRONE STREAMS. BUEHNER

&&

.AVIATION...AN UPPER LEVEL TROUGH WILL GIVE LIGHT SOUTHWEST FLOW
ALOFT OVER WESTERN WASHINGTON TODAY. LOW LEVEL OFFSHORE FLOW WILL
EASE AS A SURFACE TROUGH MOVES ONSHORE AND RIDGING EAST OF THE
CASCADES WEAKENS. THE AIR MASS WILL REMAIN MOIST AND STABLE WITH
AREAS OF VERY LIGHT PRECIPITATION MOVING THROUGH AT TIMES.

STRATUS OVER THE SOUTHWEST INTERIOR OVERNIGHT IS ERODING AS HIGHER
LEVEL MOISTURE ASSOCIATED WITH INCOMING TROUGH INCREASES. A FEW
POCKETS OF SURFACE VSBYS 3-5SM COULD PERSIST AROUND KOLM THROUGH
15Z. MAINLY VFR CEILINGS EXPECTED THIS MORNING...BUT MODELS INDICATE
THE LOW LEVELS WILL MOISTEN UP LATER TODAY WITH SOME HIGHER END MVFR
CEILINGS POSSIBLE MIDDAY INTO THE EVENING AS LIGHT PRECIP ASSOCIATED
WITH TROUGH MOVES INLAND.

KSEA...VFR CEILINGS EXPECTED THROUGH LATE MORNING...BUT MAY SEE SOME
TEMPO BKN-OVC030 WITH LIGHT RAIN 18Z-00Z. MVFR CEILINGS MAY STICK
AROUND TONIGHT WITH LIGHT SURFACE GRADIENTS AND MOIST AIR MASS IN
PLACE. EAST-SOUTHEAST WIND 5 TO 10 KNOTS...BECOMING LIGHT SOUTHERLY
TONIGHT.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES
CONTINUE FOR THE OUTER COASTAL WATERS WHERE SEAS REMAIN NEAR 10
FEET. FOR THE REMAINDER OF THE WATERS...A PERIOD OF QUIET WEATHER IS
FORECAST TODAY WITH A WEAK SURFACE TROUGH OVER THE REGION. A BETTER
ORGANIZED AND STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY.
A GALE WATCH FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY
NIGHT REMAINS IN EFFECT FOR THIS. ANOTHER FRONT ON SATURDAY COULD
PRODUCES GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY TODAY FOR HAZARDOUS SEAS OUTER COASTAL
     WATERS.
     SMALL CRAFT ADVISORY TODAY FOR ROUGH GRAYS HARBOR BAR.
     GALE WATCH THURSDAY MORNING THROUGH LATE THURSDAY NIGHT FOR THE
     COASTAL WATERS.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML









000
FXUS66 KPQR 171059
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
259 AM PST WED DEC 17 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND EVENTUALLY MOVE ONSHORE ALONG THE N OR/S WA COAST
THIS AFTERNOON. THIS WILL MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY
OVER THE HIGHER TERRAIN THIS MORNING. AN UPPER LEVEL SHORTWAVE WILL
PUSH ONSHORE LATER TODAY...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST...WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.SHORT TERM...TODAY THROUGH SATURDAY...VERY LIGHT RAIN CONTINUES TO
IMPACT SW WASHINGTON THIS MORNING BUT HAS OTHERWISE STARTED TO
DISSIPATE OVER THE SOUTHERN PORTION OF THE FORECAST AREA. WATER VAPOR
IMAGERY SHOWS A CLOSED LOW WEAKENING AS IT HAS PUSHED ONSHORE NEAR
THE OREGON/CALIFORNIA BORDER...WHILE AN UPPER LEVEL SHORTWAVE IS
ELONGATING AS IT APPROACHES THE PACIFIC NORTHWEST COASTLINE. NOT MUCH
CHANGE IN THE KTTD-KDLS GRADIENT...WHICH REMAINS AROUND -5 EARLY THIS
MORNING. EAST WINDS CONTINUE TO GUST NEAR 25 MPH THROUGH THE
GORGE...BUT EXPECT THE EASTERLY GRADIENT TO WEAKEN BY LATE TONIGHT.

AFTER A PERIOD OF LIGHT RAIN THIS MORNING...MODELS REMAIN CONSISTENT
IN SHOWING AN UPTICK IN PRECIP BY THIS AFTERNOON ASSOCIATED WITH THE
VORT MAX JUST OFFSHORE AROUND 45N 134W. THE LOWER LEVEL MOISTURE
ASSOCIATED WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING
FROM THE SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP THIS
EVENING AND THROUGH TONIGHT. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY.

WITH CLEARING SKIES AND LIGHT WINDS...SHOULD SEE SOME SHALLOW FOG TO
DEVELOP IN INTERIOR VALLEYS TONIGHT THROUGH EARLY THU MORNING. MODELS
MAINTAIN A THREAT FOR LIGHT PRECIP OVER THE HIGHER TERRAIN MUCH OF
THU...BUT OTHERWISE EXPECT DRY CONDITIONS TO PERSIST TO LOWER
ELEVATIONS. THE NEXT SIGNIFICANT FRONTAL SYSTEM ARRIVES LATE
THU...SPREADING RAIN AND BRINGING GUSTY COASTAL WINDS TO THE REGION
THROUGH FRI. PRECIPITABLE WATER IS EXPECTED TO BE NEAR AN INCH AND AN
APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND EXPECT THE
HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE COAST AND COAST
RANGE THROUGH MIDDAY FRI. OTHER LOCATIONS WILL SEE ON AVERAGE 0.5
INCHES OF RAIN. SNOW LEVELS SHOULD REMAIN ABOVE 5000 FEET DURING THE
PEAK RAIN PERIOD...BUT LOWER TO NEAR OR BELOW THE CASCADE PASSES
BEHIND THE FRONT FRIDAY AFTERNOON.

STRONG LOW PRESSURE OVER THE GULF OF ALASKA WILL PUSH INLAND LATE FRI
INTO EARLY SAT MORNING...SIMULTANEOUSLY FLATTENING A BROAD AREA OF
HIGH PRESSURE OVER THE EASTERN PACIFIC. THERE IS INCREASING
CONFIDENCE AN ATMOSPHERIC RIVER SCENARIO WILL SET UP...WITH ABUNDANT
MOISTURE AIMED DIRECTLY AT THE PACIFIC NORTHWEST SAT.

.LONG TERM...SATURDAY NIGHT THROUGH TUESDAY...AS THIS TROUGH MOVES ON
SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES ONSHORE AND STALLS
EAST-TO-WEST ACROSS NORTHWEST OREGON AND SOUTHWEST WASHINGTON. THIS
PUTS OUR AREA IN THE PATH OF RAIN STARTING SATURDAY THROUGH MONDAY.
SOME UNCERTAINTY EXISTS IN WHERE THIS BOUNDARY WILL SET UP...WHICH
WILL DETERMINE HOW MUCH RAINFALL WE WILL GET. ON TUESDAY...GEFS
ENSEMBLE SPAGHETTI PLOTS GET MESSY AND SIGNIFICANT DIFFERENCES START
TO SHOW UP BETWEEN THE GFS AND ECMWF...DECREASING CONFIDENCE ON HOW
THE REST OF THE WEEK WILL SHAPE UP.  AS OF NOW...THE MOST COMMON
SOLUTION IS THAT HIGH PRESSURE RIDGING WILL START TO BUILD BACK OVER
THE WESTERN U.S. WHICH SUGGESTS DRIER WEATHER STARTING TUESDAY...
THOUGH UNCERTAINTY IS VERY HIGH. -MCCOY

&&

.AVIATION...VFR CONDITIONS TO PERSIST AT MOST TAF SITES THROUGH
WEDNESDAY AFTERNOON. THE QUESTION STILL REMAINS WHETHER LOW LEVEL
STRATUS/FOG WILL DEVELOP IN THE CENTRAL AND SOUTH WILLAMETTE
VALLEY. IF LOW LEVEL STRATUS/FOG DOES DEVELOP EXPECT IT TO CLEAR
OUT BY EARLY WEDNESDAY AFTERNOON. BRIEF PERIODS OF MVFR TO IFR
CIGS AND VIS ARE POSSIBLE UNDER LIGHT TO MODERATE RAIN BANDS
THROUGH LATE WEDNESDAY. WITH CLEARING EXPECTED LATE WEDNESDAY WE
WILL LIKELY SEE THE DEVELOPMENT OF IFR CIGS AND VIS DUE TO LOW
LEVEL STRATUS/FOG RETURNING TO PORTIONS OF THE VALLEY.

KPDX AND APPROACHES...VFR CONDITIONS TO PERSIST WEDNESDAY.
HOWEVER...BRIEF PERIODS OF MVFR CIGS AND VIS ARE POSSIBLE UNDER
LIGHT TO MODERATE RAIN BANDS THROUGH WEDNESDAY AFTERNOON. /64

&&

.MARINE...RATHER BENIGN CONDITIONS TO CONTINUE THROUGH EARLY
THURSDAY AS A WEAK LOW PRESSURE SYSTEM MOVES INLAND OVER NORTHERN
CALIFORNIA. EXPECT SEAS TO REMAIN BELOW 10 FT WITH GUST TO 20 KT
POSSIBLE. ANOTHER LOW PRESSURE SYSTEM CONTINUES TO STRENGTHEN
OFFSHORE AND LOOKS TO MOVE ACROSS THE COASTAL WATERS ON THURSDAY.
THIS SYSTEM WILL LIKELY BRING SOUTHERLY GALES THURSDAY THROUGH
EARLY FRIDAY...BUT THERE IS STILL SOME UNCERTAINTY ON THE EXACT
TIMING. SEAS WITH THIS SYSTEM ARE EXPECTED TO BUILD INTO THE UPPER
TEENS TO THE LOW 20S BY SATURDAY MORNING. AN ACTIVE WEATHER
PATTERN WILL CONTINUE THROUGH NEXT WEEK AND COULD BRING MORE
SOUTHERLY GALES AND ELEVATED SEAS. /64

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

WA...NONE.

PZ...GALE WATCH FROM THURSDAY MORNING THROUGH THURSDAY EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 11 AM
    THIS MORNING TO 4 PM PST THIS AFTERNOON.

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KOTX 171024
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
223 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Today through Thursday night...The region will continue to be
under the influence of a split and ragged upper level trough
today and tonight. Again a couple of weak waves will move through
the forecast area and result in periods of light precipitation.
Cooler air banked up against the Cascades continues to make snow
level forecast a challenge. The 00z guidance came in with wet bulb
temperatures down around 30F when in fact the wet bulbs are in the
low to mid 30s. I most likely kept snow levels a little to low
across the areas for this morning, otherwise snow levels are
anywhere from 2500 to around 4000 feet across the area. So any
precipitation will be valley rain...possibly mixed with a little
snow for the Methow and up near Ardnevoir and mountain snow.
Precipitation amounts will remain light with a few hundredths in
the basin and lower valleys and possibly up to a tenth in the
mountains. Snow accumulations even for the mountains will only be
an inch or two.

Precipitation chances will then be on the decrease from the west
for the remainder of the night and Thursday as a short lived ridge
of high pressure builds into the region. Some pops were kept in
the orographically favored Panhandle mountains, but again
accumulations should remain light with light snow above 3500 feet
for the Panhandle. Fog and stratus will likely develop through
the night and Thursday morning with a saturated boundary layer and
light south-southwest winds.

The next system will move towards the region Thursday night and
increase Pacific moisture. Snow levels for the valleys near the
Cascades will again be problematic. I don`t see any freezing rain
at this time but precipitation probably as a snow or snow/rain mix
for those valleys and snow above 3000-3500 feet. Some of the
higher locations in the Cascades could see 3-5 inches of fresh
snow by early Friday morning. Tobin

Friday and Friday night...The next in a series of Pacific weather
systems pushes across the Inland Northwest on Friday with a warm
front followed closely by an occluded front Friday evening. This
one looks to be a little stronger and a little warmer.
Precipitation type will be tricky with light snow in the morning,
turning to valley rain and mountain snow by afternoon. There looks
to be the potential for up to an inch in the northern valleys,
while the northern mountains could see 1-3 inches. Drying occurs
behind the front Friday night with a brief break in the
precipitation and light winds.

Saturday through Sunday night...This still looks to be a wettest
period as an atmospheric river takes aim on the Pacific NW. The
GFS and ECMWF show agreement of moderate isentropic lift spreading
across the region Saturday morning with a stream of plentiful
moisture for most of the weekend. Again precipitation type will be
tricky, initially with valley snow possible in the valley northern
valleys especially in the Cascade valleys. Warming increases
Saturday night into Sunday, making it a mainly rain/high mountain
snow event by Sunday afternoon. The 850mb 0C line pushes to the
Canadian border on Sunday while temps of +5C to +7C poke into the
Columbia Basin. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. Moderate to heavy rainfall
is possible with juicy QPF amounts of 0.25" to 0.40" during a 24
hour period Saturday night into Sunday. Winds will increase by
Sunday evening with speeds 25-35 kts across the Columbia Basin.
Could even see some gusty mountain winds across the Cascades by
Sunday night. POPs and QPF amounts have been raised and winds
bumped for this period.

Monday through Tuesday...A cold front slides through the region
Monday allowing the atmospheric river to sag southward and cooler
drier air to filter in from the north. The bulk of the precipitation
will be found in the Cascades and Panhandle mountains through
Monday morning and then gradually taper off. Drier conditions and
clearing will allow temperatures to cool Monday night. This will
set the stage for the next weather system. Under the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. A warm front will spread light precipitation across
eastern Washington by Tuesday. Based on low level temperatures,
there is good chance that the precipitation type will start off as
snow for most areas. /rfox.

&&

.AVIATION...
06Z TAFS: Lingering snow showers or flurries will continue
overnight north of the Spokane/Coeur d`Alene corridor. Fog and
stratus that developed across this area is already beginning to
lift as drier northeasterly winds scour out this low level
moisture. There will continue to be a slight chance for some
patchy fog tonight at KGEG, KSFF and KCOE, but the trend is for
improving flight conditions overnight. The same cannot be said
for KMWH and KEAT which will see a stratus deck through the
overnight hours into Wednesday. Another shortwave disturbance
will push across the region on Wednesday. Light rain is expected
at KEAT and KMWH by the morning hours with light rain developing
at KGEG, KSFF and KCOE in the afternoon. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 /  50  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$




000
FXUS66 KOTX 171024
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
223 AM PST WED DEC 17 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Today through Thursday night...The region will continue to be
under the influence of a split and ragged upper level trough
today and tonight. Again a couple of weak waves will move through
the forecast area and result in periods of light precipitation.
Cooler air banked up against the Cascades continues to make snow
level forecast a challenge. The 00z guidance came in with wet bulb
temperatures down around 30F when in fact the wet bulbs are in the
low to mid 30s. I most likely kept snow levels a little to low
across the areas for this morning, otherwise snow levels are
anywhere from 2500 to around 4000 feet across the area. So any
precipitation will be valley rain...possibly mixed with a little
snow for the Methow and up near Ardnevoir and mountain snow.
Precipitation amounts will remain light with a few hundredths in
the basin and lower valleys and possibly up to a tenth in the
mountains. Snow accumulations even for the mountains will only be
an inch or two.

Precipitation chances will then be on the decrease from the west
for the remainder of the night and Thursday as a short lived ridge
of high pressure builds into the region. Some pops were kept in
the orographically favored Panhandle mountains, but again
accumulations should remain light with light snow above 3500 feet
for the Panhandle. Fog and stratus will likely develop through
the night and Thursday morning with a saturated boundary layer and
light south-southwest winds.

The next system will move towards the region Thursday night and
increase Pacific moisture. Snow levels for the valleys near the
Cascades will again be problematic. I don`t see any freezing rain
at this time but precipitation probably as a snow or snow/rain mix
for those valleys and snow above 3000-3500 feet. Some of the
higher locations in the Cascades could see 3-5 inches of fresh
snow by early Friday morning. Tobin

Friday and Friday night...The next in a series of Pacific weather
systems pushes across the Inland Northwest on Friday with a warm
front followed closely by an occluded front Friday evening. This
one looks to be a little stronger and a little warmer.
Precipitation type will be tricky with light snow in the morning,
turning to valley rain and mountain snow by afternoon. There looks
to be the potential for up to an inch in the northern valleys,
while the northern mountains could see 1-3 inches. Drying occurs
behind the front Friday night with a brief break in the
precipitation and light winds.

Saturday through Sunday night...This still looks to be a wettest
period as an atmospheric river takes aim on the Pacific NW. The
GFS and ECMWF show agreement of moderate isentropic lift spreading
across the region Saturday morning with a stream of plentiful
moisture for most of the weekend. Again precipitation type will be
tricky, initially with valley snow possible in the valley northern
valleys especially in the Cascade valleys. Warming increases
Saturday night into Sunday, making it a mainly rain/high mountain
snow event by Sunday afternoon. The 850mb 0C line pushes to the
Canadian border on Sunday while temps of +5C to +7C poke into the
Columbia Basin. Sunday appears to be the warmest day with
widespread 40s and a few 50s possible. Moderate to heavy rainfall
is possible with juicy QPF amounts of 0.25" to 0.40" during a 24
hour period Saturday night into Sunday. Winds will increase by
Sunday evening with speeds 25-35 kts across the Columbia Basin.
Could even see some gusty mountain winds across the Cascades by
Sunday night. POPs and QPF amounts have been raised and winds
bumped for this period.

Monday through Tuesday...A cold front slides through the region
Monday allowing the atmospheric river to sag southward and cooler
drier air to filter in from the north. The bulk of the precipitation
will be found in the Cascades and Panhandle mountains through
Monday morning and then gradually taper off. Drier conditions and
clearing will allow temperatures to cool Monday night. This will
set the stage for the next weather system. Under the northwest
flow aloft, a disturbance is expected to drop down from the Gulf
of Alaska. A warm front will spread light precipitation across
eastern Washington by Tuesday. Based on low level temperatures,
there is good chance that the precipitation type will start off as
snow for most areas. /rfox.

&&

.AVIATION...
06Z TAFS: Lingering snow showers or flurries will continue
overnight north of the Spokane/Coeur d`Alene corridor. Fog and
stratus that developed across this area is already beginning to
lift as drier northeasterly winds scour out this low level
moisture. There will continue to be a slight chance for some
patchy fog tonight at KGEG, KSFF and KCOE, but the trend is for
improving flight conditions overnight. The same cannot be said
for KMWH and KEAT which will see a stratus deck through the
overnight hours into Wednesday. Another shortwave disturbance
will push across the region on Wednesday. Light rain is expected
at KEAT and KMWH by the morning hours with light rain developing
at KGEG, KSFF and KCOE in the afternoon. /SVH

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        39  32  37  32  39  31 /  20  40  30  20  80  20
Coeur d`Alene  39  33  38  33  39  32 /  10  50  60  20  80  30
Pullman        43  33  43  34  42  29 /  10  50  40  10  70  20
Lewiston       43  35  45  36  44  31 /  10  40  30  10  60  20
Colville       35  32  37  33  38  32 /  20  50  30  50  80  20
Sandpoint      37  32  37  31  36  32 /  20  60  60  30  80  30
Kellogg        37  32  38  31  36  31 /  10  70  70  20  80  40
Moses Lake     39  29  39  32  42  28 /  20  20  10  60  60  10
Wenatchee      38  31  37  32  40  30 /  50  30  10  70  50  10
Omak           34  27  34  30  37  27 /  40  40  10  70  80  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 170551
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
951 PM PST TUE DEC 16 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Evening forecast update to increase precip chances, decrease snow
levels and increase overnight low temperatures. Increased moist
isentropic ascent out ahead of a weak upper level feature has
resulted in widespread light snowfall along and north of the
Highway 2 corridor. Snowflakes will be very fine and contain
have a small moisture content; as a result, I do not anticipated
much if any accumulations from the snow. Best chances for
accumulations will be on grassy surfaces across the northern
mountains where less than a half of an inch will fall over most
locations. Snow will begin to push north of the Spokane/Coeur
d`Alene corridor late this evening.

With current dew point temperatures in the low to mid 30s across
the basin early this evening, I increase low temperatures a bit
warming them into the 30s for most locations. Fog will be possible
due how moist the boundary layer is. Easterly winds may result in
less fog in the Panhandle and portions of extreme easter WA with
better chances for a foggy morning expected in the western basin,
Cascade valleys and northern mtn valleys. /SVH


&&

.AVIATION...
06Z TAFS: Lingering snow showers or flurries will continue
overnight north of the Spokane/Coeur d`Alene corridor. Fog and
stratus that developed across this area is already beginning to
lift as drier northeasterly winds scour out this low level
moisture. There will continue to be a slight chance for some
patchy fog tonight at KGEG, KSFF and KCOE, but the trend is for
improving flight conditions overnight. The same cannot be said
for KMWH and KEAT which will see a stratus deck through the
overnight hours into Wednesday. Another shortwave disturbance
will push across the region on Wednesday. Light rain is expected
at KEAT and KMWH by the morning hours with light rain developing
at KGEG, KSFF and KCOE in the afternoon. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        30  38  33  36  33  38 /  70  30  40  30  20  70
Coeur d`Alene  30  40  33  37  31  38 /  60  30  50  50  20  70
Pullman        32  42  34  42  33  41 /  10  10  50  30  20  70
Lewiston       34  42  35  45  34  43 /  10  10  40  30  10  50
Colville       30  36  33  37  33  37 /  70  30  40  30  50  70
Sandpoint      29  36  33  37  30  36 /  50  30  60  60  20  80
Kellogg        31  38  32  38  29  37 /  20  10  70  60  20  70
Moses Lake     32  38  29  38  34  41 /  10  30  20  10  60  50
Wenatchee      34  37  30  37  33  40 /  50  30  30  10  60  50
Omak           29  34  28  34  32  37 /  70  40  40  10  70  60

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 170551
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
951 PM PST TUE DEC 16 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Evening forecast update to increase precip chances, decrease snow
levels and increase overnight low temperatures. Increased moist
isentropic ascent out ahead of a weak upper level feature has
resulted in widespread light snowfall along and north of the
Highway 2 corridor. Snowflakes will be very fine and contain
have a small moisture content; as a result, I do not anticipated
much if any accumulations from the snow. Best chances for
accumulations will be on grassy surfaces across the northern
mountains where less than a half of an inch will fall over most
locations. Snow will begin to push north of the Spokane/Coeur
d`Alene corridor late this evening.

With current dew point temperatures in the low to mid 30s across
the basin early this evening, I increase low temperatures a bit
warming them into the 30s for most locations. Fog will be possible
due how moist the boundary layer is. Easterly winds may result in
less fog in the Panhandle and portions of extreme easter WA with
better chances for a foggy morning expected in the western basin,
Cascade valleys and northern mtn valleys. /SVH


&&

.AVIATION...
06Z TAFS: Lingering snow showers or flurries will continue
overnight north of the Spokane/Coeur d`Alene corridor. Fog and
stratus that developed across this area is already beginning to
lift as drier northeasterly winds scour out this low level
moisture. There will continue to be a slight chance for some
patchy fog tonight at KGEG, KSFF and KCOE, but the trend is for
improving flight conditions overnight. The same cannot be said
for KMWH and KEAT which will see a stratus deck through the
overnight hours into Wednesday. Another shortwave disturbance
will push across the region on Wednesday. Light rain is expected
at KEAT and KMWH by the morning hours with light rain developing
at KGEG, KSFF and KCOE in the afternoon. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        30  38  33  36  33  38 /  70  30  40  30  20  70
Coeur d`Alene  30  40  33  37  31  38 /  60  30  50  50  20  70
Pullman        32  42  34  42  33  41 /  10  10  50  30  20  70
Lewiston       34  42  35  45  34  43 /  10  10  40  30  10  50
Colville       30  36  33  37  33  37 /  70  30  40  30  50  70
Sandpoint      29  36  33  37  30  36 /  50  30  60  60  20  80
Kellogg        31  38  32  38  29  37 /  20  10  70  60  20  70
Moses Lake     32  38  29  38  34  41 /  10  30  20  10  60  50
Wenatchee      34  37  30  37  33  40 /  50  30  30  10  60  50
Omak           29  34  28  34  32  37 /  70  40  40  10  70  60

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 170551
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
951 PM PST TUE DEC 16 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Evening forecast update to increase precip chances, decrease snow
levels and increase overnight low temperatures. Increased moist
isentropic ascent out ahead of a weak upper level feature has
resulted in widespread light snowfall along and north of the
Highway 2 corridor. Snowflakes will be very fine and contain
have a small moisture content; as a result, I do not anticipated
much if any accumulations from the snow. Best chances for
accumulations will be on grassy surfaces across the northern
mountains where less than a half of an inch will fall over most
locations. Snow will begin to push north of the Spokane/Coeur
d`Alene corridor late this evening.

With current dew point temperatures in the low to mid 30s across
the basin early this evening, I increase low temperatures a bit
warming them into the 30s for most locations. Fog will be possible
due how moist the boundary layer is. Easterly winds may result in
less fog in the Panhandle and portions of extreme easter WA with
better chances for a foggy morning expected in the western basin,
Cascade valleys and northern mtn valleys. /SVH


&&

.AVIATION...
06Z TAFS: Lingering snow showers or flurries will continue
overnight north of the Spokane/Coeur d`Alene corridor. Fog and
stratus that developed across this area is already beginning to
lift as drier northeasterly winds scour out this low level
moisture. There will continue to be a slight chance for some
patchy fog tonight at KGEG, KSFF and KCOE, but the trend is for
improving flight conditions overnight. The same cannot be said
for KMWH and KEAT which will see a stratus deck through the
overnight hours into Wednesday. Another shortwave disturbance
will push across the region on Wednesday. Light rain is expected
at KEAT and KMWH by the morning hours with light rain developing
at KGEG, KSFF and KCOE in the afternoon. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        30  38  33  36  33  38 /  70  30  40  30  20  70
Coeur d`Alene  30  40  33  37  31  38 /  60  30  50  50  20  70
Pullman        32  42  34  42  33  41 /  10  10  50  30  20  70
Lewiston       34  42  35  45  34  43 /  10  10  40  30  10  50
Colville       30  36  33  37  33  37 /  70  30  40  30  50  70
Sandpoint      29  36  33  37  30  36 /  50  30  60  60  20  80
Kellogg        31  38  32  38  29  37 /  20  10  70  60  20  70
Moses Lake     32  38  29  38  34  41 /  10  30  20  10  60  50
Wenatchee      34  37  30  37  33  40 /  50  30  30  10  60  50
Omak           29  34  28  34  32  37 /  70  40  40  10  70  60

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KOTX 170551
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
951 PM PST TUE DEC 16 2014

.SYNOPSIS...
A more active weather pattern will develop through the week with
periods of light snow in the mountains...and rain or snow in the
valleys. Lower elevations from Interstate 90 south will see mainly
rain...while areas in the Cascades and near the Canadian border
will remain mainly snow. A much stronger weather system over the
weekend will usher in warmer temperatures with sharply rising snow
levels...as well as the potential for windy conditions.


&&

.DISCUSSION...
Evening forecast update to increase precip chances, decrease snow
levels and increase overnight low temperatures. Increased moist
isentropic ascent out ahead of a weak upper level feature has
resulted in widespread light snowfall along and north of the
Highway 2 corridor. Snowflakes will be very fine and contain
have a small moisture content; as a result, I do not anticipated
much if any accumulations from the snow. Best chances for
accumulations will be on grassy surfaces across the northern
mountains where less than a half of an inch will fall over most
locations. Snow will begin to push north of the Spokane/Coeur
d`Alene corridor late this evening.

With current dew point temperatures in the low to mid 30s across
the basin early this evening, I increase low temperatures a bit
warming them into the 30s for most locations. Fog will be possible
due how moist the boundary layer is. Easterly winds may result in
less fog in the Panhandle and portions of extreme easter WA with
better chances for a foggy morning expected in the western basin,
Cascade valleys and northern mtn valleys. /SVH


&&

.AVIATION...
06Z TAFS: Lingering snow showers or flurries will continue
overnight north of the Spokane/Coeur d`Alene corridor. Fog and
stratus that developed across this area is already beginning to
lift as drier northeasterly winds scour out this low level
moisture. There will continue to be a slight chance for some
patchy fog tonight at KGEG, KSFF and KCOE, but the trend is for
improving flight conditions overnight. The same cannot be said
for KMWH and KEAT which will see a stratus deck through the
overnight hours into Wednesday. Another shortwave disturbance
will push across the region on Wednesday. Light rain is expected
at KEAT and KMWH by the morning hours with light rain developing
at KGEG, KSFF and KCOE in the afternoon. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        30  38  33  36  33  38 /  70  30  40  30  20  70
Coeur d`Alene  30  40  33  37  31  38 /  60  30  50  50  20  70
Pullman        32  42  34  42  33  41 /  10  10  50  30  20  70
Lewiston       34  42  35  45  34  43 /  10  10  40  30  10  50
Colville       30  36  33  37  33  37 /  70  30  40  30  50  70
Sandpoint      29  36  33  37  30  36 /  50  30  60  60  20  80
Kellogg        31  38  32  38  29  37 /  20  10  70  60  20  70
Moses Lake     32  38  29  38  34  41 /  10  30  20  10  60  50
Wenatchee      34  37  30  37  33  40 /  50  30  30  10  60  50
Omak           29  34  28  34  32  37 /  70  40  40  10  70  60

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Air Stagnation Advisory until Noon PST Friday for East Slopes
     Northern Cascades-Moses Lake Area-Northeast Mountains-
     Okanogan Highlands-Okanogan Valley-Upper Columbia Basin-
     Waterville Plateau-Wenatchee Area.

&&

$$





000
FXUS66 KPQR 170511
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
912 PM PST TUE DEC 16 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND PUSH NORTHWARD OVERNIGHT...EVENTUALLY MOVING
ONSHORE ALONG THE N OR/S WA COAST TOMORROW AFTERNOON. THIS WILL
MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY OVER THE HIGHER TERRAIN
OVERNIGHT AND TOMORROW MORNING. AN UPPER LEVEL SHORTWAVE WILL PUSH
ONSHORE LATER TOMORROW...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST...WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.EVENING UPDATE...A LOW PRES CIRCULATION IS APPARENT ON SATELLITE AND
RADAR IMAGERY THIS EVENING JUST OFFSHORE OF THE CA/OR BORDER. WATER
VAPOR SATELLITE SHOWS MOISTURE SPREADING NORTHWARD FROM THIS SYSTEM
INTO NW OREGON AND SW WASHINGTON. THERE ARE ALSO LIGHT ECHOES SHOWING
UP ON RADAR OVER THE SOUTHERN AND WESTERN PORTIONS OF OUR FCST
AREA...BUT LITTLE TO NO RAIN IS REACHING THE GROUND AT THIS TIME.
EXPECT AS THE NIGHT GOES ON AND THE OFFSHORE LOW SLOWLY MOVES
NORTHEAST...WE WILL SEE LIGHT PRECIPITATION START TO REACH THE
SURFACE...ESPECIALLY OVER THE HIGHER TERRAIN. A WEAK VORT MAX WILL
ALSO MOVE ONSHORE EARLY WED MORNING...WHICH MAY HELP AID THE SHOWERS.

THE MAIN CHANGE TO THE FCST THIS EVENING WAS TO INCREASE POPS AND QPF
FROM THE 18Z WED TO 12Z THU TIME FRAME. THE CLOSED LOW JUST OFFSHORE
TONIGHT WILL SLOWLY WEAKEN AND PUSH ONSHORE AROUND MIDDAY TOMORROW.
MEANWHILE...THE SHORTWAVE NOW APPARENT ON WATER VAPOR SATELLITE
NEARING 45N 140W IS MODELED TO STRETCH OUT AND PUSH ONSHORE LATER
TOMORROW AFTERNOON AND EVENING. THE LOWER LEVEL MOISTURE ASSOCIATED
WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING FROM THE
SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP LATER TOMORROW
AND TOMORROW NIGHT. THE 00Z NAM AND GFS RUNS PICKED UP ON THIS
PERIOD OF ENHANCED PRECIP. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY. PYLE

.PREV DISC ISSUED 231 PM PST TUE DEC 17...

.SHORT TERM...TONIGHT THROUGH FRIDAY...SHOWERS HAVE PRETTY MUCH ENDED
OVER THE PORTLAND FORECAST AREA EARLY THIS AFTERNOON...EXCEPT FOR
VERY INFREQUENT ISOLATED SHOWER OVER THE SW WASHINGTON CASCADES.
SATELLITE IMAGERY SHOWS A SURFACE LOW AROUND 150 MILES WEST OF THE
SOUTHERN OREGON COAST...NEAR 42N 127W. THE HIGHER RESOLUTION
MODELS...HRRR AND RAP INITIALIZE BEST WITH THE LOW AND FORECAST RAIN
MOVING NORTH INTO LANE COUNTY SLIGHTLY EARLIER THAN THE OTHER MODELS.
HAVE TRENDED TOWARDS THIS EARLIER ARRIVAL...BUT ONLY HAVE FAIR
CONFIDENCE THAT THE TIMING WILL PAN OUT. ANY RAIN LATE THIS AFTERNOON
SHOULD BE FAIRLY LIGHT AND REMAIN WEST OF THE SOUTH AND CENTRAL
WILLAMETTE VALLEY.

THE LOW WILL MOVE CLOSER TO THE SOUTHERN OREGON COAST LATE THIS
AFTERNOON AND EVENING THEN MOVE ONTO THE CENTRAL OREGON COAST AS AN
UPPER TROUGH LATE TONIGHT...WITH SHOWERS MAINLY OVER THE HIGHER
TERRAIN THROUGH WEDNESDAY MORNING. SOME CLEARING EARLY WED MORNING
MAY RESULT IN SHALLOW FOG AND LOW CLOUDS IN SOME OF THE INTERIOR
VALLEYS...MAINLY SOUTH OF SALEM.

EASTERLY WINDS HAVE HELD ON TODAY WITH A TROUTDALE TO DALLES PRESSURE
GRADIENT HOLDING AROUND 5 MB. THIS GRADIENT SHOULD TIGHTEN A LITTLE
THIS EVENING AS THE LOW MOVES CLOSER TO THE COAST AND MAINTAIN GUSTS
AROUND 30 MPH THROUGH THE WESTERN COLUMBIA RIVER GORGE.

SHOWERS WILL CONTINUE WEDNESDAY...MAINLY FOR THE HIGHER TERRAIN AS
THE PARENT UPPER LEVEL TROUGH MOVES OVER THE PACIFIC NW. SHOWERS
SHOULD END OVERNIGHT AS AN UPPER RIDGE BUILDS OVER THE AREA AND
EXPECT THAT CLEARING SKIES AND LIGHT WINDS WILL LEAD TO SHALLOW FOG
FOR THE INTERIOR VALLEYS EARLY THURSDAY MORNING. MOST OF THURSDAY
WILL BE DRY WITH AN INCREASE OF MID AN HIGH LEVEL CLOUDS IN THE
AFTERNOON.

MODELS ARE IN GOOD AGREEMENT THAT A WELL ORGANIZED FRONT WILL BRING
GUSTY WINDS TO THE COAST THURSDAY EVENING WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. PRECIPITABLE WATER IS EXPECTED TO BE NEAR
AN INCH AND AN APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND
EXPECT THE HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE
COAST AND COAST RANGE THURSDAY NIGHT THROUGH FRIDAY MORNING. OTHER
AREAS SHOULD SEE BETWEEN 0.4 AND 0.60 INCH OF RAIN. SNOW LEVELS
SHOULD REMAIN ABOVE 5000 FEET DURING THE PEAK RAIN PERIOD...BUT LOWER
TO NEAR OR BELOW THE CASCADE PASSES BEHIND THE FRONT FRIDAY
AFTERNOON.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...A BROAD RIDGE OF HIGH
PRESSURE OVER THE WESTERN U.S. FLATTENS AS A STRONG LOW PRESSURE
SYSTEM OVER THE GULF OF ALASKA MOVES INLAND TO OUR NORTH. AS THIS
TROUGH MOVES ON SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES
ONSHORE AND STALLS EAST-TO-WEST ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON. THIS PUTS OUR AREA IN THE PATH OF RAIN
STARTING SATURDAY THROUGH MONDAY. SOME UNCERTAINTY EXISTS IN WHERE
THIS BOUNDARY WILL SET UP...WHICH WILL DETERMINE HOW MUCH RAINFALL
WE WILL GET. ON TUESDAY...GEFS ENSEMBLE SPAGHETTI PLOTS GET MESSY
AND SIGNIFICANT DIFFERENCES START TO SHOW UP BETWEEN THE GFS AND
ECMWF...DECREASING CONFIDENCE ON HOW THE REST OF THE WEEK WILL SHAPE
UP.  AS OF NOW...THE MOST COMMON SOLUTION IS THAT HIGH PRESSURE
RIDGING WILL START TO BUILD BACK OVER THE WESTERN U.S. WHICH
SUGGESTS DRIER WEATHER STARTING TUESDAY...THOUGH UNCERTAINTY IS VERY
HIGH. -MCCOY

&&

.AVIATION...MOIST SOUTHERLY FLOW ALOFT...WITH PLENTY OF MID AND
HIGH CLOUDS OVER REGION. DO HAVE AREAS OF MVFR CIGS ALONG THE
COAST AND WILL SEE THOSE PERSIST OVERNIGHT INTO WED AM. QUESTION
IS WHETHER OR NOT LOW CLOUDS REFORM S OF SALEM TONIGHT. HAVE
CLEARED OUT AT MOMENT...WITH STILL RATHER HIGH HUMIDITY. SO
SUSPECT WITH OCCASIONAL LIGHT RAIN THERE...WILL SEE AREAS OF IFR
STRATUS REFORM TONIGHT TO SOUTH OF KSLE.

KPDX AND APPROACHES...VFR WILL PERSIST TONIGHT AND WED...BUT CIGS
LOWER TO 5K FT LATER AFTER 09Z WITH OCCASIONAL LIGHT RAIN THROUGH
17Z. VFR WITH LOT OF MID AND HIGH CLOUDS ON WED.ROCKEY.
 &&

.MARINE...NOT MUCH CHANGE. GRADIENTS WEAKENING THIS EVENING AS
LOW HEADS INTO N CALIF. STILL...WILL GET A GUSTS TO 25 KT ON THE
OUTER SOUTH WATERS THIS EVENING. SEAS HOLDING AT 8 TO 9 FT.

NEXT SYSTEM NOW DEVELOPING WAY OFFSHORE BETWEEN 160W-170W. THIS
SYSTEM WILL BRING SOUTHERLY GALES TO THE WATERS LATER THU THROUGH
EARLY FRI AM. STILL SOME UNCERTAINTY ON EXACT TIMING AND DETAILS
BUT WILL BE VERY ACTIVE PERIOD. SEAS LIKELY TO PUSH BACK INTO THE
UPPER TEENS TO NEAR 20 FT BY FRI AM.

MORE FRONTS ARRIVE THIS WEEKEND INTO EARLY NEXT WEEK...WITH
SOUTHERLY GALES LIKELY AND ENHANCED SEAS.   ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FOR THU AND THU NIGHT ON ALL COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR TONIGHT
AND AGAIN 11 AM TO 4 PM WED.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 170511
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
912 PM PST TUE DEC 16 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND PUSH NORTHWARD OVERNIGHT...EVENTUALLY MOVING
ONSHORE ALONG THE N OR/S WA COAST TOMORROW AFTERNOON. THIS WILL
MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY OVER THE HIGHER TERRAIN
OVERNIGHT AND TOMORROW MORNING. AN UPPER LEVEL SHORTWAVE WILL PUSH
ONSHORE LATER TOMORROW...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST...WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.EVENING UPDATE...A LOW PRES CIRCULATION IS APPARENT ON SATELLITE AND
RADAR IMAGERY THIS EVENING JUST OFFSHORE OF THE CA/OR BORDER. WATER
VAPOR SATELLITE SHOWS MOISTURE SPREADING NORTHWARD FROM THIS SYSTEM
INTO NW OREGON AND SW WASHINGTON. THERE ARE ALSO LIGHT ECHOES SHOWING
UP ON RADAR OVER THE SOUTHERN AND WESTERN PORTIONS OF OUR FCST
AREA...BUT LITTLE TO NO RAIN IS REACHING THE GROUND AT THIS TIME.
EXPECT AS THE NIGHT GOES ON AND THE OFFSHORE LOW SLOWLY MOVES
NORTHEAST...WE WILL SEE LIGHT PRECIPITATION START TO REACH THE
SURFACE...ESPECIALLY OVER THE HIGHER TERRAIN. A WEAK VORT MAX WILL
ALSO MOVE ONSHORE EARLY WED MORNING...WHICH MAY HELP AID THE SHOWERS.

THE MAIN CHANGE TO THE FCST THIS EVENING WAS TO INCREASE POPS AND QPF
FROM THE 18Z WED TO 12Z THU TIME FRAME. THE CLOSED LOW JUST OFFSHORE
TONIGHT WILL SLOWLY WEAKEN AND PUSH ONSHORE AROUND MIDDAY TOMORROW.
MEANWHILE...THE SHORTWAVE NOW APPARENT ON WATER VAPOR SATELLITE
NEARING 45N 140W IS MODELED TO STRETCH OUT AND PUSH ONSHORE LATER
TOMORROW AFTERNOON AND EVENING. THE LOWER LEVEL MOISTURE ASSOCIATED
WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING FROM THE
SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP LATER TOMORROW
AND TOMORROW NIGHT. THE 00Z NAM AND GFS RUNS PICKED UP ON THIS
PERIOD OF ENHANCED PRECIP. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY. PYLE

.PREV DISC ISSUED 231 PM PST TUE DEC 17...

.SHORT TERM...TONIGHT THROUGH FRIDAY...SHOWERS HAVE PRETTY MUCH ENDED
OVER THE PORTLAND FORECAST AREA EARLY THIS AFTERNOON...EXCEPT FOR
VERY INFREQUENT ISOLATED SHOWER OVER THE SW WASHINGTON CASCADES.
SATELLITE IMAGERY SHOWS A SURFACE LOW AROUND 150 MILES WEST OF THE
SOUTHERN OREGON COAST...NEAR 42N 127W. THE HIGHER RESOLUTION
MODELS...HRRR AND RAP INITIALIZE BEST WITH THE LOW AND FORECAST RAIN
MOVING NORTH INTO LANE COUNTY SLIGHTLY EARLIER THAN THE OTHER MODELS.
HAVE TRENDED TOWARDS THIS EARLIER ARRIVAL...BUT ONLY HAVE FAIR
CONFIDENCE THAT THE TIMING WILL PAN OUT. ANY RAIN LATE THIS AFTERNOON
SHOULD BE FAIRLY LIGHT AND REMAIN WEST OF THE SOUTH AND CENTRAL
WILLAMETTE VALLEY.

THE LOW WILL MOVE CLOSER TO THE SOUTHERN OREGON COAST LATE THIS
AFTERNOON AND EVENING THEN MOVE ONTO THE CENTRAL OREGON COAST AS AN
UPPER TROUGH LATE TONIGHT...WITH SHOWERS MAINLY OVER THE HIGHER
TERRAIN THROUGH WEDNESDAY MORNING. SOME CLEARING EARLY WED MORNING
MAY RESULT IN SHALLOW FOG AND LOW CLOUDS IN SOME OF THE INTERIOR
VALLEYS...MAINLY SOUTH OF SALEM.

EASTERLY WINDS HAVE HELD ON TODAY WITH A TROUTDALE TO DALLES PRESSURE
GRADIENT HOLDING AROUND 5 MB. THIS GRADIENT SHOULD TIGHTEN A LITTLE
THIS EVENING AS THE LOW MOVES CLOSER TO THE COAST AND MAINTAIN GUSTS
AROUND 30 MPH THROUGH THE WESTERN COLUMBIA RIVER GORGE.

SHOWERS WILL CONTINUE WEDNESDAY...MAINLY FOR THE HIGHER TERRAIN AS
THE PARENT UPPER LEVEL TROUGH MOVES OVER THE PACIFIC NW. SHOWERS
SHOULD END OVERNIGHT AS AN UPPER RIDGE BUILDS OVER THE AREA AND
EXPECT THAT CLEARING SKIES AND LIGHT WINDS WILL LEAD TO SHALLOW FOG
FOR THE INTERIOR VALLEYS EARLY THURSDAY MORNING. MOST OF THURSDAY
WILL BE DRY WITH AN INCREASE OF MID AN HIGH LEVEL CLOUDS IN THE
AFTERNOON.

MODELS ARE IN GOOD AGREEMENT THAT A WELL ORGANIZED FRONT WILL BRING
GUSTY WINDS TO THE COAST THURSDAY EVENING WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. PRECIPITABLE WATER IS EXPECTED TO BE NEAR
AN INCH AND AN APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND
EXPECT THE HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE
COAST AND COAST RANGE THURSDAY NIGHT THROUGH FRIDAY MORNING. OTHER
AREAS SHOULD SEE BETWEEN 0.4 AND 0.60 INCH OF RAIN. SNOW LEVELS
SHOULD REMAIN ABOVE 5000 FEET DURING THE PEAK RAIN PERIOD...BUT LOWER
TO NEAR OR BELOW THE CASCADE PASSES BEHIND THE FRONT FRIDAY
AFTERNOON.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...A BROAD RIDGE OF HIGH
PRESSURE OVER THE WESTERN U.S. FLATTENS AS A STRONG LOW PRESSURE
SYSTEM OVER THE GULF OF ALASKA MOVES INLAND TO OUR NORTH. AS THIS
TROUGH MOVES ON SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES
ONSHORE AND STALLS EAST-TO-WEST ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON. THIS PUTS OUR AREA IN THE PATH OF RAIN
STARTING SATURDAY THROUGH MONDAY. SOME UNCERTAINTY EXISTS IN WHERE
THIS BOUNDARY WILL SET UP...WHICH WILL DETERMINE HOW MUCH RAINFALL
WE WILL GET. ON TUESDAY...GEFS ENSEMBLE SPAGHETTI PLOTS GET MESSY
AND SIGNIFICANT DIFFERENCES START TO SHOW UP BETWEEN THE GFS AND
ECMWF...DECREASING CONFIDENCE ON HOW THE REST OF THE WEEK WILL SHAPE
UP.  AS OF NOW...THE MOST COMMON SOLUTION IS THAT HIGH PRESSURE
RIDGING WILL START TO BUILD BACK OVER THE WESTERN U.S. WHICH
SUGGESTS DRIER WEATHER STARTING TUESDAY...THOUGH UNCERTAINTY IS VERY
HIGH. -MCCOY

&&

.AVIATION...MOIST SOUTHERLY FLOW ALOFT...WITH PLENTY OF MID AND
HIGH CLOUDS OVER REGION. DO HAVE AREAS OF MVFR CIGS ALONG THE
COAST AND WILL SEE THOSE PERSIST OVERNIGHT INTO WED AM. QUESTION
IS WHETHER OR NOT LOW CLOUDS REFORM S OF SALEM TONIGHT. HAVE
CLEARED OUT AT MOMENT...WITH STILL RATHER HIGH HUMIDITY. SO
SUSPECT WITH OCCASIONAL LIGHT RAIN THERE...WILL SEE AREAS OF IFR
STRATUS REFORM TONIGHT TO SOUTH OF KSLE.

KPDX AND APPROACHES...VFR WILL PERSIST TONIGHT AND WED...BUT CIGS
LOWER TO 5K FT LATER AFTER 09Z WITH OCCASIONAL LIGHT RAIN THROUGH
17Z. VFR WITH LOT OF MID AND HIGH CLOUDS ON WED.ROCKEY.
 &&

.MARINE...NOT MUCH CHANGE. GRADIENTS WEAKENING THIS EVENING AS
LOW HEADS INTO N CALIF. STILL...WILL GET A GUSTS TO 25 KT ON THE
OUTER SOUTH WATERS THIS EVENING. SEAS HOLDING AT 8 TO 9 FT.

NEXT SYSTEM NOW DEVELOPING WAY OFFSHORE BETWEEN 160W-170W. THIS
SYSTEM WILL BRING SOUTHERLY GALES TO THE WATERS LATER THU THROUGH
EARLY FRI AM. STILL SOME UNCERTAINTY ON EXACT TIMING AND DETAILS
BUT WILL BE VERY ACTIVE PERIOD. SEAS LIKELY TO PUSH BACK INTO THE
UPPER TEENS TO NEAR 20 FT BY FRI AM.

MORE FRONTS ARRIVE THIS WEEKEND INTO EARLY NEXT WEEK...WITH
SOUTHERLY GALES LIKELY AND ENHANCED SEAS.   ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FOR THU AND THU NIGHT ON ALL COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR TONIGHT
AND AGAIN 11 AM TO 4 PM WED.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 170511
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
912 PM PST TUE DEC 16 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND PUSH NORTHWARD OVERNIGHT...EVENTUALLY MOVING
ONSHORE ALONG THE N OR/S WA COAST TOMORROW AFTERNOON. THIS WILL
MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY OVER THE HIGHER TERRAIN
OVERNIGHT AND TOMORROW MORNING. AN UPPER LEVEL SHORTWAVE WILL PUSH
ONSHORE LATER TOMORROW...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST...WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.EVENING UPDATE...A LOW PRES CIRCULATION IS APPARENT ON SATELLITE AND
RADAR IMAGERY THIS EVENING JUST OFFSHORE OF THE CA/OR BORDER. WATER
VAPOR SATELLITE SHOWS MOISTURE SPREADING NORTHWARD FROM THIS SYSTEM
INTO NW OREGON AND SW WASHINGTON. THERE ARE ALSO LIGHT ECHOES SHOWING
UP ON RADAR OVER THE SOUTHERN AND WESTERN PORTIONS OF OUR FCST
AREA...BUT LITTLE TO NO RAIN IS REACHING THE GROUND AT THIS TIME.
EXPECT AS THE NIGHT GOES ON AND THE OFFSHORE LOW SLOWLY MOVES
NORTHEAST...WE WILL SEE LIGHT PRECIPITATION START TO REACH THE
SURFACE...ESPECIALLY OVER THE HIGHER TERRAIN. A WEAK VORT MAX WILL
ALSO MOVE ONSHORE EARLY WED MORNING...WHICH MAY HELP AID THE SHOWERS.

THE MAIN CHANGE TO THE FCST THIS EVENING WAS TO INCREASE POPS AND QPF
FROM THE 18Z WED TO 12Z THU TIME FRAME. THE CLOSED LOW JUST OFFSHORE
TONIGHT WILL SLOWLY WEAKEN AND PUSH ONSHORE AROUND MIDDAY TOMORROW.
MEANWHILE...THE SHORTWAVE NOW APPARENT ON WATER VAPOR SATELLITE
NEARING 45N 140W IS MODELED TO STRETCH OUT AND PUSH ONSHORE LATER
TOMORROW AFTERNOON AND EVENING. THE LOWER LEVEL MOISTURE ASSOCIATED
WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING FROM THE
SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP LATER TOMORROW
AND TOMORROW NIGHT. THE 00Z NAM AND GFS RUNS PICKED UP ON THIS
PERIOD OF ENHANCED PRECIP. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY. PYLE

.PREV DISC ISSUED 231 PM PST TUE DEC 17...

.SHORT TERM...TONIGHT THROUGH FRIDAY...SHOWERS HAVE PRETTY MUCH ENDED
OVER THE PORTLAND FORECAST AREA EARLY THIS AFTERNOON...EXCEPT FOR
VERY INFREQUENT ISOLATED SHOWER OVER THE SW WASHINGTON CASCADES.
SATELLITE IMAGERY SHOWS A SURFACE LOW AROUND 150 MILES WEST OF THE
SOUTHERN OREGON COAST...NEAR 42N 127W. THE HIGHER RESOLUTION
MODELS...HRRR AND RAP INITIALIZE BEST WITH THE LOW AND FORECAST RAIN
MOVING NORTH INTO LANE COUNTY SLIGHTLY EARLIER THAN THE OTHER MODELS.
HAVE TRENDED TOWARDS THIS EARLIER ARRIVAL...BUT ONLY HAVE FAIR
CONFIDENCE THAT THE TIMING WILL PAN OUT. ANY RAIN LATE THIS AFTERNOON
SHOULD BE FAIRLY LIGHT AND REMAIN WEST OF THE SOUTH AND CENTRAL
WILLAMETTE VALLEY.

THE LOW WILL MOVE CLOSER TO THE SOUTHERN OREGON COAST LATE THIS
AFTERNOON AND EVENING THEN MOVE ONTO THE CENTRAL OREGON COAST AS AN
UPPER TROUGH LATE TONIGHT...WITH SHOWERS MAINLY OVER THE HIGHER
TERRAIN THROUGH WEDNESDAY MORNING. SOME CLEARING EARLY WED MORNING
MAY RESULT IN SHALLOW FOG AND LOW CLOUDS IN SOME OF THE INTERIOR
VALLEYS...MAINLY SOUTH OF SALEM.

EASTERLY WINDS HAVE HELD ON TODAY WITH A TROUTDALE TO DALLES PRESSURE
GRADIENT HOLDING AROUND 5 MB. THIS GRADIENT SHOULD TIGHTEN A LITTLE
THIS EVENING AS THE LOW MOVES CLOSER TO THE COAST AND MAINTAIN GUSTS
AROUND 30 MPH THROUGH THE WESTERN COLUMBIA RIVER GORGE.

SHOWERS WILL CONTINUE WEDNESDAY...MAINLY FOR THE HIGHER TERRAIN AS
THE PARENT UPPER LEVEL TROUGH MOVES OVER THE PACIFIC NW. SHOWERS
SHOULD END OVERNIGHT AS AN UPPER RIDGE BUILDS OVER THE AREA AND
EXPECT THAT CLEARING SKIES AND LIGHT WINDS WILL LEAD TO SHALLOW FOG
FOR THE INTERIOR VALLEYS EARLY THURSDAY MORNING. MOST OF THURSDAY
WILL BE DRY WITH AN INCREASE OF MID AN HIGH LEVEL CLOUDS IN THE
AFTERNOON.

MODELS ARE IN GOOD AGREEMENT THAT A WELL ORGANIZED FRONT WILL BRING
GUSTY WINDS TO THE COAST THURSDAY EVENING WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. PRECIPITABLE WATER IS EXPECTED TO BE NEAR
AN INCH AND AN APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND
EXPECT THE HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE
COAST AND COAST RANGE THURSDAY NIGHT THROUGH FRIDAY MORNING. OTHER
AREAS SHOULD SEE BETWEEN 0.4 AND 0.60 INCH OF RAIN. SNOW LEVELS
SHOULD REMAIN ABOVE 5000 FEET DURING THE PEAK RAIN PERIOD...BUT LOWER
TO NEAR OR BELOW THE CASCADE PASSES BEHIND THE FRONT FRIDAY
AFTERNOON.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...A BROAD RIDGE OF HIGH
PRESSURE OVER THE WESTERN U.S. FLATTENS AS A STRONG LOW PRESSURE
SYSTEM OVER THE GULF OF ALASKA MOVES INLAND TO OUR NORTH. AS THIS
TROUGH MOVES ON SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES
ONSHORE AND STALLS EAST-TO-WEST ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON. THIS PUTS OUR AREA IN THE PATH OF RAIN
STARTING SATURDAY THROUGH MONDAY. SOME UNCERTAINTY EXISTS IN WHERE
THIS BOUNDARY WILL SET UP...WHICH WILL DETERMINE HOW MUCH RAINFALL
WE WILL GET. ON TUESDAY...GEFS ENSEMBLE SPAGHETTI PLOTS GET MESSY
AND SIGNIFICANT DIFFERENCES START TO SHOW UP BETWEEN THE GFS AND
ECMWF...DECREASING CONFIDENCE ON HOW THE REST OF THE WEEK WILL SHAPE
UP.  AS OF NOW...THE MOST COMMON SOLUTION IS THAT HIGH PRESSURE
RIDGING WILL START TO BUILD BACK OVER THE WESTERN U.S. WHICH
SUGGESTS DRIER WEATHER STARTING TUESDAY...THOUGH UNCERTAINTY IS VERY
HIGH. -MCCOY

&&

.AVIATION...MOIST SOUTHERLY FLOW ALOFT...WITH PLENTY OF MID AND
HIGH CLOUDS OVER REGION. DO HAVE AREAS OF MVFR CIGS ALONG THE
COAST AND WILL SEE THOSE PERSIST OVERNIGHT INTO WED AM. QUESTION
IS WHETHER OR NOT LOW CLOUDS REFORM S OF SALEM TONIGHT. HAVE
CLEARED OUT AT MOMENT...WITH STILL RATHER HIGH HUMIDITY. SO
SUSPECT WITH OCCASIONAL LIGHT RAIN THERE...WILL SEE AREAS OF IFR
STRATUS REFORM TONIGHT TO SOUTH OF KSLE.

KPDX AND APPROACHES...VFR WILL PERSIST TONIGHT AND WED...BUT CIGS
LOWER TO 5K FT LATER AFTER 09Z WITH OCCASIONAL LIGHT RAIN THROUGH
17Z. VFR WITH LOT OF MID AND HIGH CLOUDS ON WED.ROCKEY.
 &&

.MARINE...NOT MUCH CHANGE. GRADIENTS WEAKENING THIS EVENING AS
LOW HEADS INTO N CALIF. STILL...WILL GET A GUSTS TO 25 KT ON THE
OUTER SOUTH WATERS THIS EVENING. SEAS HOLDING AT 8 TO 9 FT.

NEXT SYSTEM NOW DEVELOPING WAY OFFSHORE BETWEEN 160W-170W. THIS
SYSTEM WILL BRING SOUTHERLY GALES TO THE WATERS LATER THU THROUGH
EARLY FRI AM. STILL SOME UNCERTAINTY ON EXACT TIMING AND DETAILS
BUT WILL BE VERY ACTIVE PERIOD. SEAS LIKELY TO PUSH BACK INTO THE
UPPER TEENS TO NEAR 20 FT BY FRI AM.

MORE FRONTS ARRIVE THIS WEEKEND INTO EARLY NEXT WEEK...WITH
SOUTHERLY GALES LIKELY AND ENHANCED SEAS.   ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FOR THU AND THU NIGHT ON ALL COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR TONIGHT
AND AGAIN 11 AM TO 4 PM WED.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 170511
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
912 PM PST TUE DEC 16 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND PUSH NORTHWARD OVERNIGHT...EVENTUALLY MOVING
ONSHORE ALONG THE N OR/S WA COAST TOMORROW AFTERNOON. THIS WILL
MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY OVER THE HIGHER TERRAIN
OVERNIGHT AND TOMORROW MORNING. AN UPPER LEVEL SHORTWAVE WILL PUSH
ONSHORE LATER TOMORROW...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST...WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.EVENING UPDATE...A LOW PRES CIRCULATION IS APPARENT ON SATELLITE AND
RADAR IMAGERY THIS EVENING JUST OFFSHORE OF THE CA/OR BORDER. WATER
VAPOR SATELLITE SHOWS MOISTURE SPREADING NORTHWARD FROM THIS SYSTEM
INTO NW OREGON AND SW WASHINGTON. THERE ARE ALSO LIGHT ECHOES SHOWING
UP ON RADAR OVER THE SOUTHERN AND WESTERN PORTIONS OF OUR FCST
AREA...BUT LITTLE TO NO RAIN IS REACHING THE GROUND AT THIS TIME.
EXPECT AS THE NIGHT GOES ON AND THE OFFSHORE LOW SLOWLY MOVES
NORTHEAST...WE WILL SEE LIGHT PRECIPITATION START TO REACH THE
SURFACE...ESPECIALLY OVER THE HIGHER TERRAIN. A WEAK VORT MAX WILL
ALSO MOVE ONSHORE EARLY WED MORNING...WHICH MAY HELP AID THE SHOWERS.

THE MAIN CHANGE TO THE FCST THIS EVENING WAS TO INCREASE POPS AND QPF
FROM THE 18Z WED TO 12Z THU TIME FRAME. THE CLOSED LOW JUST OFFSHORE
TONIGHT WILL SLOWLY WEAKEN AND PUSH ONSHORE AROUND MIDDAY TOMORROW.
MEANWHILE...THE SHORTWAVE NOW APPARENT ON WATER VAPOR SATELLITE
NEARING 45N 140W IS MODELED TO STRETCH OUT AND PUSH ONSHORE LATER
TOMORROW AFTERNOON AND EVENING. THE LOWER LEVEL MOISTURE ASSOCIATED
WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING FROM THE
SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP LATER TOMORROW
AND TOMORROW NIGHT. THE 00Z NAM AND GFS RUNS PICKED UP ON THIS
PERIOD OF ENHANCED PRECIP. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY. PYLE

.PREV DISC ISSUED 231 PM PST TUE DEC 17...

.SHORT TERM...TONIGHT THROUGH FRIDAY...SHOWERS HAVE PRETTY MUCH ENDED
OVER THE PORTLAND FORECAST AREA EARLY THIS AFTERNOON...EXCEPT FOR
VERY INFREQUENT ISOLATED SHOWER OVER THE SW WASHINGTON CASCADES.
SATELLITE IMAGERY SHOWS A SURFACE LOW AROUND 150 MILES WEST OF THE
SOUTHERN OREGON COAST...NEAR 42N 127W. THE HIGHER RESOLUTION
MODELS...HRRR AND RAP INITIALIZE BEST WITH THE LOW AND FORECAST RAIN
MOVING NORTH INTO LANE COUNTY SLIGHTLY EARLIER THAN THE OTHER MODELS.
HAVE TRENDED TOWARDS THIS EARLIER ARRIVAL...BUT ONLY HAVE FAIR
CONFIDENCE THAT THE TIMING WILL PAN OUT. ANY RAIN LATE THIS AFTERNOON
SHOULD BE FAIRLY LIGHT AND REMAIN WEST OF THE SOUTH AND CENTRAL
WILLAMETTE VALLEY.

THE LOW WILL MOVE CLOSER TO THE SOUTHERN OREGON COAST LATE THIS
AFTERNOON AND EVENING THEN MOVE ONTO THE CENTRAL OREGON COAST AS AN
UPPER TROUGH LATE TONIGHT...WITH SHOWERS MAINLY OVER THE HIGHER
TERRAIN THROUGH WEDNESDAY MORNING. SOME CLEARING EARLY WED MORNING
MAY RESULT IN SHALLOW FOG AND LOW CLOUDS IN SOME OF THE INTERIOR
VALLEYS...MAINLY SOUTH OF SALEM.

EASTERLY WINDS HAVE HELD ON TODAY WITH A TROUTDALE TO DALLES PRESSURE
GRADIENT HOLDING AROUND 5 MB. THIS GRADIENT SHOULD TIGHTEN A LITTLE
THIS EVENING AS THE LOW MOVES CLOSER TO THE COAST AND MAINTAIN GUSTS
AROUND 30 MPH THROUGH THE WESTERN COLUMBIA RIVER GORGE.

SHOWERS WILL CONTINUE WEDNESDAY...MAINLY FOR THE HIGHER TERRAIN AS
THE PARENT UPPER LEVEL TROUGH MOVES OVER THE PACIFIC NW. SHOWERS
SHOULD END OVERNIGHT AS AN UPPER RIDGE BUILDS OVER THE AREA AND
EXPECT THAT CLEARING SKIES AND LIGHT WINDS WILL LEAD TO SHALLOW FOG
FOR THE INTERIOR VALLEYS EARLY THURSDAY MORNING. MOST OF THURSDAY
WILL BE DRY WITH AN INCREASE OF MID AN HIGH LEVEL CLOUDS IN THE
AFTERNOON.

MODELS ARE IN GOOD AGREEMENT THAT A WELL ORGANIZED FRONT WILL BRING
GUSTY WINDS TO THE COAST THURSDAY EVENING WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. PRECIPITABLE WATER IS EXPECTED TO BE NEAR
AN INCH AND AN APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND
EXPECT THE HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE
COAST AND COAST RANGE THURSDAY NIGHT THROUGH FRIDAY MORNING. OTHER
AREAS SHOULD SEE BETWEEN 0.4 AND 0.60 INCH OF RAIN. SNOW LEVELS
SHOULD REMAIN ABOVE 5000 FEET DURING THE PEAK RAIN PERIOD...BUT LOWER
TO NEAR OR BELOW THE CASCADE PASSES BEHIND THE FRONT FRIDAY
AFTERNOON.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...A BROAD RIDGE OF HIGH
PRESSURE OVER THE WESTERN U.S. FLATTENS AS A STRONG LOW PRESSURE
SYSTEM OVER THE GULF OF ALASKA MOVES INLAND TO OUR NORTH. AS THIS
TROUGH MOVES ON SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES
ONSHORE AND STALLS EAST-TO-WEST ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON. THIS PUTS OUR AREA IN THE PATH OF RAIN
STARTING SATURDAY THROUGH MONDAY. SOME UNCERTAINTY EXISTS IN WHERE
THIS BOUNDARY WILL SET UP...WHICH WILL DETERMINE HOW MUCH RAINFALL
WE WILL GET. ON TUESDAY...GEFS ENSEMBLE SPAGHETTI PLOTS GET MESSY
AND SIGNIFICANT DIFFERENCES START TO SHOW UP BETWEEN THE GFS AND
ECMWF...DECREASING CONFIDENCE ON HOW THE REST OF THE WEEK WILL SHAPE
UP.  AS OF NOW...THE MOST COMMON SOLUTION IS THAT HIGH PRESSURE
RIDGING WILL START TO BUILD BACK OVER THE WESTERN U.S. WHICH
SUGGESTS DRIER WEATHER STARTING TUESDAY...THOUGH UNCERTAINTY IS VERY
HIGH. -MCCOY

&&

.AVIATION...MOIST SOUTHERLY FLOW ALOFT...WITH PLENTY OF MID AND
HIGH CLOUDS OVER REGION. DO HAVE AREAS OF MVFR CIGS ALONG THE
COAST AND WILL SEE THOSE PERSIST OVERNIGHT INTO WED AM. QUESTION
IS WHETHER OR NOT LOW CLOUDS REFORM S OF SALEM TONIGHT. HAVE
CLEARED OUT AT MOMENT...WITH STILL RATHER HIGH HUMIDITY. SO
SUSPECT WITH OCCASIONAL LIGHT RAIN THERE...WILL SEE AREAS OF IFR
STRATUS REFORM TONIGHT TO SOUTH OF KSLE.

KPDX AND APPROACHES...VFR WILL PERSIST TONIGHT AND WED...BUT CIGS
LOWER TO 5K FT LATER AFTER 09Z WITH OCCASIONAL LIGHT RAIN THROUGH
17Z. VFR WITH LOT OF MID AND HIGH CLOUDS ON WED.ROCKEY.
 &&

.MARINE...NOT MUCH CHANGE. GRADIENTS WEAKENING THIS EVENING AS
LOW HEADS INTO N CALIF. STILL...WILL GET A GUSTS TO 25 KT ON THE
OUTER SOUTH WATERS THIS EVENING. SEAS HOLDING AT 8 TO 9 FT.

NEXT SYSTEM NOW DEVELOPING WAY OFFSHORE BETWEEN 160W-170W. THIS
SYSTEM WILL BRING SOUTHERLY GALES TO THE WATERS LATER THU THROUGH
EARLY FRI AM. STILL SOME UNCERTAINTY ON EXACT TIMING AND DETAILS
BUT WILL BE VERY ACTIVE PERIOD. SEAS LIKELY TO PUSH BACK INTO THE
UPPER TEENS TO NEAR 20 FT BY FRI AM.

MORE FRONTS ARRIVE THIS WEEKEND INTO EARLY NEXT WEEK...WITH
SOUTHERLY GALES LIKELY AND ENHANCED SEAS.   ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FOR THU AND THU NIGHT ON ALL COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR TONIGHT
AND AGAIN 11 AM TO 4 PM WED.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.




000
FXUS66 KPQR 170511
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
912 PM PST TUE DEC 16 2014

.SYNOPSIS...A CLOSED LOW JUST OFFSHORE WEST OF THE OR/CA BORDER WILL
SLOWLY WEAKEN AND PUSH NORTHWARD OVERNIGHT...EVENTUALLY MOVING
ONSHORE ALONG THE N OR/S WA COAST TOMORROW AFTERNOON. THIS WILL
MAINTAIN LIGHT SHOWER ACTIVITY...MAINLY OVER THE HIGHER TERRAIN
OVERNIGHT AND TOMORROW MORNING. AN UPPER LEVEL SHORTWAVE WILL PUSH
ONSHORE LATER TOMORROW...LIKELY BRINGING A PERIOD OF STEADIER
RAINFALL THROUGH EARLY THU MORNING. EXPECT A FAIRLY QUIET PERIOD FOR
MUCH OF THE DAY THU...BUT THEN A MORE ORGANIZED FRONT WILL BRING
GUSTY WINDS AND LARGE SURF TO THE COAST...WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. RISING SNOW LEVELS WILL LIMIT SNOW TO THE
HIGHEST PEAKS...BUT COLDER AIR BEHIND THE FRONT MAY RESULT IN SOME
SNOW SHOWERS FOR THE CASCADES PASSES FRIDAY EVENING AND SATURDAY.
WARMER AND MOISTER WEATHER IS EXPECTED THIS WEEKEND. THERE IS THE
POTENTIAL FOR AN ATMOSPHERIC RIVER TYPE SET UP AND ASSOCIATED HEAVY
RAIN TO DEVELOP OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.EVENING UPDATE...A LOW PRES CIRCULATION IS APPARENT ON SATELLITE AND
RADAR IMAGERY THIS EVENING JUST OFFSHORE OF THE CA/OR BORDER. WATER
VAPOR SATELLITE SHOWS MOISTURE SPREADING NORTHWARD FROM THIS SYSTEM
INTO NW OREGON AND SW WASHINGTON. THERE ARE ALSO LIGHT ECHOES SHOWING
UP ON RADAR OVER THE SOUTHERN AND WESTERN PORTIONS OF OUR FCST
AREA...BUT LITTLE TO NO RAIN IS REACHING THE GROUND AT THIS TIME.
EXPECT AS THE NIGHT GOES ON AND THE OFFSHORE LOW SLOWLY MOVES
NORTHEAST...WE WILL SEE LIGHT PRECIPITATION START TO REACH THE
SURFACE...ESPECIALLY OVER THE HIGHER TERRAIN. A WEAK VORT MAX WILL
ALSO MOVE ONSHORE EARLY WED MORNING...WHICH MAY HELP AID THE SHOWERS.

THE MAIN CHANGE TO THE FCST THIS EVENING WAS TO INCREASE POPS AND QPF
FROM THE 18Z WED TO 12Z THU TIME FRAME. THE CLOSED LOW JUST OFFSHORE
TONIGHT WILL SLOWLY WEAKEN AND PUSH ONSHORE AROUND MIDDAY TOMORROW.
MEANWHILE...THE SHORTWAVE NOW APPARENT ON WATER VAPOR SATELLITE
NEARING 45N 140W IS MODELED TO STRETCH OUT AND PUSH ONSHORE LATER
TOMORROW AFTERNOON AND EVENING. THE LOWER LEVEL MOISTURE ASSOCIATED
WITH THE SURFACE LOW COMBINED WITH THE UPPER LEVEL FORCING FROM THE
SHORTWAVE SHOULD DRIVE A PERIOD OF STEADIER PRECIP LATER TOMORROW
AND TOMORROW NIGHT. THE 00Z NAM AND GFS RUNS PICKED UP ON THIS
PERIOD OF ENHANCED PRECIP. THE VORT MAX PUSHES EAST OF THE CASCADES
BY 12Z THU...AFTER WHICH SHOWER ACTIVITY SHOULD DROP OFF
SIGNIFICANTLY. PYLE

.PREV DISC ISSUED 231 PM PST TUE DEC 17...

.SHORT TERM...TONIGHT THROUGH FRIDAY...SHOWERS HAVE PRETTY MUCH ENDED
OVER THE PORTLAND FORECAST AREA EARLY THIS AFTERNOON...EXCEPT FOR
VERY INFREQUENT ISOLATED SHOWER OVER THE SW WASHINGTON CASCADES.
SATELLITE IMAGERY SHOWS A SURFACE LOW AROUND 150 MILES WEST OF THE
SOUTHERN OREGON COAST...NEAR 42N 127W. THE HIGHER RESOLUTION
MODELS...HRRR AND RAP INITIALIZE BEST WITH THE LOW AND FORECAST RAIN
MOVING NORTH INTO LANE COUNTY SLIGHTLY EARLIER THAN THE OTHER MODELS.
HAVE TRENDED TOWARDS THIS EARLIER ARRIVAL...BUT ONLY HAVE FAIR
CONFIDENCE THAT THE TIMING WILL PAN OUT. ANY RAIN LATE THIS AFTERNOON
SHOULD BE FAIRLY LIGHT AND REMAIN WEST OF THE SOUTH AND CENTRAL
WILLAMETTE VALLEY.

THE LOW WILL MOVE CLOSER TO THE SOUTHERN OREGON COAST LATE THIS
AFTERNOON AND EVENING THEN MOVE ONTO THE CENTRAL OREGON COAST AS AN
UPPER TROUGH LATE TONIGHT...WITH SHOWERS MAINLY OVER THE HIGHER
TERRAIN THROUGH WEDNESDAY MORNING. SOME CLEARING EARLY WED MORNING
MAY RESULT IN SHALLOW FOG AND LOW CLOUDS IN SOME OF THE INTERIOR
VALLEYS...MAINLY SOUTH OF SALEM.

EASTERLY WINDS HAVE HELD ON TODAY WITH A TROUTDALE TO DALLES PRESSURE
GRADIENT HOLDING AROUND 5 MB. THIS GRADIENT SHOULD TIGHTEN A LITTLE
THIS EVENING AS THE LOW MOVES CLOSER TO THE COAST AND MAINTAIN GUSTS
AROUND 30 MPH THROUGH THE WESTERN COLUMBIA RIVER GORGE.

SHOWERS WILL CONTINUE WEDNESDAY...MAINLY FOR THE HIGHER TERRAIN AS
THE PARENT UPPER LEVEL TROUGH MOVES OVER THE PACIFIC NW. SHOWERS
SHOULD END OVERNIGHT AS AN UPPER RIDGE BUILDS OVER THE AREA AND
EXPECT THAT CLEARING SKIES AND LIGHT WINDS WILL LEAD TO SHALLOW FOG
FOR THE INTERIOR VALLEYS EARLY THURSDAY MORNING. MOST OF THURSDAY
WILL BE DRY WITH AN INCREASE OF MID AN HIGH LEVEL CLOUDS IN THE
AFTERNOON.

MODELS ARE IN GOOD AGREEMENT THAT A WELL ORGANIZED FRONT WILL BRING
GUSTY WINDS TO THE COAST THURSDAY EVENING WITH RAIN SPREADING INLAND
THURSDAY NIGHT AND FRIDAY. PRECIPITABLE WATER IS EXPECTED TO BE NEAR
AN INCH AND AN APPROACHING JET STREAK SHOULD PROVIDE GOOD LIFT AND
EXPECT THE HIGHEST RAINFALL TOTALS OF 0.75 TO 1 INCH ACROSS THE
COAST AND COAST RANGE THURSDAY NIGHT THROUGH FRIDAY MORNING. OTHER
AREAS SHOULD SEE BETWEEN 0.4 AND 0.60 INCH OF RAIN. SNOW LEVELS
SHOULD REMAIN ABOVE 5000 FEET DURING THE PEAK RAIN PERIOD...BUT LOWER
TO NEAR OR BELOW THE CASCADE PASSES BEHIND THE FRONT FRIDAY
AFTERNOON.

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...A BROAD RIDGE OF HIGH
PRESSURE OVER THE WESTERN U.S. FLATTENS AS A STRONG LOW PRESSURE
SYSTEM OVER THE GULF OF ALASKA MOVES INLAND TO OUR NORTH. AS THIS
TROUGH MOVES ON SHORE SATURDAY...THE ASSOCIATED COLD FRONT MOVES
ONSHORE AND STALLS EAST-TO-WEST ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON. THIS PUTS OUR AREA IN THE PATH OF RAIN
STARTING SATURDAY THROUGH MONDAY. SOME UNCERTAINTY EXISTS IN WHERE
THIS BOUNDARY WILL SET UP...WHICH WILL DETERMINE HOW MUCH RAINFALL
WE WILL GET. ON TUESDAY...GEFS ENSEMBLE SPAGHETTI PLOTS GET MESSY
AND SIGNIFICANT DIFFERENCES START TO SHOW UP BETWEEN THE GFS AND
ECMWF...DECREASING CONFIDENCE ON HOW THE REST OF THE WEEK WILL SHAPE
UP.  AS OF NOW...THE MOST COMMON SOLUTION IS THAT HIGH PRESSURE
RIDGING WILL START TO BUILD BACK OVER THE WESTERN U.S. WHICH
SUGGESTS DRIER WEATHER STARTING TUESDAY...THOUGH UNCERTAINTY IS VERY
HIGH. -MCCOY

&&

.AVIATION...MOIST SOUTHERLY FLOW ALOFT...WITH PLENTY OF MID AND
HIGH CLOUDS OVER REGION. DO HAVE AREAS OF MVFR CIGS ALONG THE
COAST AND WILL SEE THOSE PERSIST OVERNIGHT INTO WED AM. QUESTION
IS WHETHER OR NOT LOW CLOUDS REFORM S OF SALEM TONIGHT. HAVE
CLEARED OUT AT MOMENT...WITH STILL RATHER HIGH HUMIDITY. SO
SUSPECT WITH OCCASIONAL LIGHT RAIN THERE...WILL SEE AREAS OF IFR
STRATUS REFORM TONIGHT TO SOUTH OF KSLE.

KPDX AND APPROACHES...VFR WILL PERSIST TONIGHT AND WED...BUT CIGS
LOWER TO 5K FT LATER AFTER 09Z WITH OCCASIONAL LIGHT RAIN THROUGH
17Z. VFR WITH LOT OF MID AND HIGH CLOUDS ON WED.ROCKEY.
 &&

.MARINE...NOT MUCH CHANGE. GRADIENTS WEAKENING THIS EVENING AS
LOW HEADS INTO N CALIF. STILL...WILL GET A GUSTS TO 25 KT ON THE
OUTER SOUTH WATERS THIS EVENING. SEAS HOLDING AT 8 TO 9 FT.

NEXT SYSTEM NOW DEVELOPING WAY OFFSHORE BETWEEN 160W-170W. THIS
SYSTEM WILL BRING SOUTHERLY GALES TO THE WATERS LATER THU THROUGH
EARLY FRI AM. STILL SOME UNCERTAINTY ON EXACT TIMING AND DETAILS
BUT WILL BE VERY ACTIVE PERIOD. SEAS LIKELY TO PUSH BACK INTO THE
UPPER TEENS TO NEAR 20 FT BY FRI AM.

MORE FRONTS ARRIVE THIS WEEKEND INTO EARLY NEXT WEEK...WITH
SOUTHERLY GALES LIKELY AND ENHANCED SEAS.   ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WATCH FOR THU AND THU NIGHT ON ALL COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR TONIGHT
AND AGAIN 11 AM TO 4 PM WED.

&&


$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.



000
FXUS66 KSEW 170452
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE DEC 16 2014

.SYNOPSIS...A WEAK TROUGH WILL BRING AREAS OF LIGHT RAIN TO WESTERN
WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER PACIFIC FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA LATE THURSDAY THROUGH FRIDAY WITH
MORE SIGNIFICANT RAIN. A WET WEATHER PATTERN WILL DEVELOP THIS
WEEKEND...WITH HEAVIER RAIN ESPECIALLY AT THE COAST AND IN THE
MOUNTAINS.

&&

.SHORT TERM...A WEAK SYSTEM IS OVER THE OFFSHORE WATERS THIS
EVENING. THE CORE OF THIS FEATURE IS MOVING INTO SOUTHERN OREGON AND
NORTHERN CALIFORNIA...LEAVING THE MUCH WEAKER PORTION OF IT OFF THE
WASHINGTON COAST. SOME PRECIPITATION IS MOVING INTO THE COASTAL
WATERS AT THIS TIME...BUT WESTERN WASHINGTON IS JUST MOSTLY CLOUDY.
TEMPERATURES AT 8 PM WERE IN THE UPPER 30S TO 40S.

THE SYSTEM OFFSHORE WILL WEAKEN FURTHER AS IT MOVES INLAND
TONIGHT...BRINGING SOME LIGHT RAIN TO MAINLY THE COAST AND OLYMPIC
PENINSULA. AREAS OF LIGHT PRECIPITATION WILL SPREAD TO THE WESTERN
WASHINGTON INTERIOR LOWLANDS AND EVENTUALLY THE CASCADES...AS THE
SYSTEM CONTINUES ITS SLOW EASTWARD PROGRESSION. THEN A WEAK UPPER
TROUGH WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY NIGHT FOR SOME
LIGHT SHOWERS.

TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD FROM TONIGHT THROUGH
WEDNESDAY NIGHT WILL GENERALLY BE 0.10 TO 0.25 INCH. THE SNOW LEVEL
WILL BE AROUND 3000 TO 3500 FT...WITH AROUND 1 TO 3 INCHES OF SNOW
IN THE MOUNTAINS.

A SMALL UPPER RIDGE WILL MOVE QUICKLY ACROSS THE FORECAST AREA ON
THURSDAY. A STRONGER FRONTAL SYSTEM WILL BRING MORE SIGNIFICANT
PRECIPITATION TO THE AREA LATE THURSDAY AND THURSDAY NIGHT...
DECREASING ON FRIDAY. STORM TOTAL PRECIPITATION WITH THAT SYSTEM
WILL BE MOSTLY 0.5 TO 1.5 INCHES IN THE MOUNTAINS AND UP TO 0.75
INCHES IN THE LOWLANDS. THE SNOW LEVEL WILL RISE TO 3500 TO 5000 FT
AS THE HEAVIEST PRECIPITATION OCCURS...SO IT COULD ACTUALLY BRING A
DECENT ROUND OF SNOWFALL TO THE SKI AREAS AND HIGHER PASSES AND
MOUNTAIN ROADS. IN ADDITION IT WILL PRODUCE LOCALLY WINDY CONDITIONS
AT THE COAST AND IN THE NORTH INTERIOR.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
DISCUSSION -- GLOBAL MODELS REMAIN IN GOOD AGREEMENT THAT A MORE
CONSOLIDATED WLY FLOW PATTERN DEVELOPS ACROSS THE PACIFIC OVER THE
WEEKEND. THE STRONG WLY JET WILL DIRECT AN ATMOSPHERIC RIVER OF
MOISTURE INTO WRN WA LATER SATURDAY THROUGH  EARLY NEXT WEEK. THE
INITIAL WARM FRONTAL WAVE WILL BRING STRONG SW FLOW ALOFT AND HEAVY
RAIN TO THE MOUNTAINS SATURDAY AFTERNOON AND NIGHT. MODELS DIFFER ON
HOW LONG THE TRAILING MOISTURE PLUM REMAINS DIRECTED INTO WRN WA.
HOWEVER...MOST MODELS SHOW AT LEAST 24-36 HOURS OF HEAVY MOUNTAIN
RAINFALL BEFORE TAPERING OFF WHICH COULD CAUSE SOME CONCERNS FOR
FLOODING ON PRONE RIVERS. SEE THE HYDRO DISCUSSION FOR FURTHER
DETAILS. RAIN AMOUNTS WILL NOT BE NEARLY HAS HEAVY IN THE LOWLANDS
WHICH SHOULD SHADOW EFFICIENTLY FROM SEATTLE/TACOMA NORTH TO EVERETT
GIVEN THE STRONG W-WSW FLOW. HIGH POPS ARE STILL WARRANTED EVEN WITH
LESS QPF AND IT WILL ALSO BE BREEZY AT TIMES...ESPECIALLY ACROSS THE
N INTERIOR/COAST WHICH IS MORE SUSCEPTIBLE TO STRONG SE SURFACE
GRADIENTS.

THE GFS/ECMWF BOTH SHOW A LULL OR BREAK IN PRECIPITATION AROUND
MONDAY OR MONDAY NIGHT. ANOTHER SURFACE LOW FEATURE TRACKS INTO WRN
WA TUESDAY WITH MORE RAIN. IF THERE IS A BREAK AS SHOWN BY CURRENT
MODELS...THEN ADDITIONAL RAINFALL WILL PROBABLY NOT BE
HYDROLOGICALLY SIGNIFICANT. IF THE LOW IS FASTER WITH LITTLE OR NO
BREAK...THEN IT WILL ADD TO FLOODING CONCERNS.

RAIN TRANSITIONS TO SHOWERS SOMETIME MID WEEK. THE 00Z RUNS OF THE
GFS/ECMWF SHOWED A COLDER NLY FLOW PATTERN DEVELOPING. 12/18Z RUNS
ARE COOL AND DRY BY WEDNESDAY BUT NOT NEARLY AS COLD. IT WILL ALL
DEPEND ON THE DEVELOPMENT OF A HIGH OVER KONA LOW. RIDGING OUTSIDE
OF 140 W WOULD DRIVE COLDER NLY FLOW OVER THE PAC NW. INSIDE 140 W
WOULD STILL LIKELY BE DRY BUT NOT AS COLD. TEMPERATURES ARE TRENDED
DOWNWARD SLIGHTLY WITH HIGHS IN THE LOWER 40S BY WEDNESDAY AND LOWS
IN THE 30S. MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
AROUND MONDAY...WITH HEAVY MOUNTAIN RAIN POSSIBLE. MODELS SHOW 3-6+
INCHES OF RAIN IN 36 HOURS FROM SATURDAY NIGHT THROUGH EARLY
MONDAY... WHICH COULD BE ENOUGH TO CAUSE FLOODING ON SOME FLOOD
PRONE RIVERS.   MCDONNAL

&&

.AVIATION...AN UPPER LEVEL TROUGH NEAR THE COAST WILL GIVE LIGHT
SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON TONIGHT AND WEDNESDAY.
LOW LEVEL OFFSHORE FLOW WILL GRADUALLY EASE AS A SURFACE TROUGH
MOVES ONSHORE AND SURFACE RIDGING EAST OF THE CASCADES WEAKENS. THE
AIR MASS WILL REMAIN MOIST AND STABLE WITH AREAS OF VERY LIGHT
PRECIPITATION MOVING THROUGH AT TIMES.

BRIEF CLEARING AND INCREASING LOW LEVEL MOISTURE WILL LEAD TO SOME
AREAS OF STRATUS AND/OR FOG OVER THE EXTREME SOUTH SOUND AND
SOUTHWEST INTERIOR OVERNIGHT WHERE SURFACE VSBYS COULD DROP BELOW
1SM AT TIMES THROUGH 15Z. FROM THE CENTRAL PUGET SOUND
NORTHWARD...MAINLY VFR CEILINGS ARE EXPECTED OVERNIGHT BUT WITH
PLENTIFUL HIGH AND MID LEVEL MOISTURE. LATEST MODELS BRING SOME
LIGHT PRECIPITATION INLAND WITH THE SURFACE TROUGH WEDNESDAY
AFTERNOON AND THERE COULD BE SOME HIGHER END MVFR CEILINGS
ASSOCIATED WITH IT.

KSEA...VFR CEILINGS BELOW 050 A TIMES OVERNIGHT INTO WEDNESDAY WITH
SOME LIGHT PRECIP POSSIBLE TOWARD DAYBREAK. EAST-SOUTHEAST WIND 5 TO
10 KNOTS.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES WILL
CONTINUE FOR THE OUTER COASTAL WATERS WHERE BORDERLINE ADVISORY
WINDS AND SEAS NEAR 10 FEET REMAIN POSSIBLE. FOR THE REMAINDER OF
THE WATERS...A PERIOD OF QUIET WEATHER IS FORECAST FOR WEDNESDAY
WITH A WEAK BROAD TROUGH OVER THE REGION. A BETTER ORGANIZED AND
STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY. A GALE WATCH
FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY NIGHT
REMAINS IN EFFECT FOR THIS. A STRONGER FRONT ON SATURDAY COULD
PRODUCE GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR ON WEDNESDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 170452
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE DEC 16 2014

.SYNOPSIS...A WEAK TROUGH WILL BRING AREAS OF LIGHT RAIN TO WESTERN
WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER PACIFIC FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA LATE THURSDAY THROUGH FRIDAY WITH
MORE SIGNIFICANT RAIN. A WET WEATHER PATTERN WILL DEVELOP THIS
WEEKEND...WITH HEAVIER RAIN ESPECIALLY AT THE COAST AND IN THE
MOUNTAINS.

&&

.SHORT TERM...A WEAK SYSTEM IS OVER THE OFFSHORE WATERS THIS
EVENING. THE CORE OF THIS FEATURE IS MOVING INTO SOUTHERN OREGON AND
NORTHERN CALIFORNIA...LEAVING THE MUCH WEAKER PORTION OF IT OFF THE
WASHINGTON COAST. SOME PRECIPITATION IS MOVING INTO THE COASTAL
WATERS AT THIS TIME...BUT WESTERN WASHINGTON IS JUST MOSTLY CLOUDY.
TEMPERATURES AT 8 PM WERE IN THE UPPER 30S TO 40S.

THE SYSTEM OFFSHORE WILL WEAKEN FURTHER AS IT MOVES INLAND
TONIGHT...BRINGING SOME LIGHT RAIN TO MAINLY THE COAST AND OLYMPIC
PENINSULA. AREAS OF LIGHT PRECIPITATION WILL SPREAD TO THE WESTERN
WASHINGTON INTERIOR LOWLANDS AND EVENTUALLY THE CASCADES...AS THE
SYSTEM CONTINUES ITS SLOW EASTWARD PROGRESSION. THEN A WEAK UPPER
TROUGH WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY NIGHT FOR SOME
LIGHT SHOWERS.

TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD FROM TONIGHT THROUGH
WEDNESDAY NIGHT WILL GENERALLY BE 0.10 TO 0.25 INCH. THE SNOW LEVEL
WILL BE AROUND 3000 TO 3500 FT...WITH AROUND 1 TO 3 INCHES OF SNOW
IN THE MOUNTAINS.

A SMALL UPPER RIDGE WILL MOVE QUICKLY ACROSS THE FORECAST AREA ON
THURSDAY. A STRONGER FRONTAL SYSTEM WILL BRING MORE SIGNIFICANT
PRECIPITATION TO THE AREA LATE THURSDAY AND THURSDAY NIGHT...
DECREASING ON FRIDAY. STORM TOTAL PRECIPITATION WITH THAT SYSTEM
WILL BE MOSTLY 0.5 TO 1.5 INCHES IN THE MOUNTAINS AND UP TO 0.75
INCHES IN THE LOWLANDS. THE SNOW LEVEL WILL RISE TO 3500 TO 5000 FT
AS THE HEAVIEST PRECIPITATION OCCURS...SO IT COULD ACTUALLY BRING A
DECENT ROUND OF SNOWFALL TO THE SKI AREAS AND HIGHER PASSES AND
MOUNTAIN ROADS. IN ADDITION IT WILL PRODUCE LOCALLY WINDY CONDITIONS
AT THE COAST AND IN THE NORTH INTERIOR.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
DISCUSSION -- GLOBAL MODELS REMAIN IN GOOD AGREEMENT THAT A MORE
CONSOLIDATED WLY FLOW PATTERN DEVELOPS ACROSS THE PACIFIC OVER THE
WEEKEND. THE STRONG WLY JET WILL DIRECT AN ATMOSPHERIC RIVER OF
MOISTURE INTO WRN WA LATER SATURDAY THROUGH  EARLY NEXT WEEK. THE
INITIAL WARM FRONTAL WAVE WILL BRING STRONG SW FLOW ALOFT AND HEAVY
RAIN TO THE MOUNTAINS SATURDAY AFTERNOON AND NIGHT. MODELS DIFFER ON
HOW LONG THE TRAILING MOISTURE PLUM REMAINS DIRECTED INTO WRN WA.
HOWEVER...MOST MODELS SHOW AT LEAST 24-36 HOURS OF HEAVY MOUNTAIN
RAINFALL BEFORE TAPERING OFF WHICH COULD CAUSE SOME CONCERNS FOR
FLOODING ON PRONE RIVERS. SEE THE HYDRO DISCUSSION FOR FURTHER
DETAILS. RAIN AMOUNTS WILL NOT BE NEARLY HAS HEAVY IN THE LOWLANDS
WHICH SHOULD SHADOW EFFICIENTLY FROM SEATTLE/TACOMA NORTH TO EVERETT
GIVEN THE STRONG W-WSW FLOW. HIGH POPS ARE STILL WARRANTED EVEN WITH
LESS QPF AND IT WILL ALSO BE BREEZY AT TIMES...ESPECIALLY ACROSS THE
N INTERIOR/COAST WHICH IS MORE SUSCEPTIBLE TO STRONG SE SURFACE
GRADIENTS.

THE GFS/ECMWF BOTH SHOW A LULL OR BREAK IN PRECIPITATION AROUND
MONDAY OR MONDAY NIGHT. ANOTHER SURFACE LOW FEATURE TRACKS INTO WRN
WA TUESDAY WITH MORE RAIN. IF THERE IS A BREAK AS SHOWN BY CURRENT
MODELS...THEN ADDITIONAL RAINFALL WILL PROBABLY NOT BE
HYDROLOGICALLY SIGNIFICANT. IF THE LOW IS FASTER WITH LITTLE OR NO
BREAK...THEN IT WILL ADD TO FLOODING CONCERNS.

RAIN TRANSITIONS TO SHOWERS SOMETIME MID WEEK. THE 00Z RUNS OF THE
GFS/ECMWF SHOWED A COLDER NLY FLOW PATTERN DEVELOPING. 12/18Z RUNS
ARE COOL AND DRY BY WEDNESDAY BUT NOT NEARLY AS COLD. IT WILL ALL
DEPEND ON THE DEVELOPMENT OF A HIGH OVER KONA LOW. RIDGING OUTSIDE
OF 140 W WOULD DRIVE COLDER NLY FLOW OVER THE PAC NW. INSIDE 140 W
WOULD STILL LIKELY BE DRY BUT NOT AS COLD. TEMPERATURES ARE TRENDED
DOWNWARD SLIGHTLY WITH HIGHS IN THE LOWER 40S BY WEDNESDAY AND LOWS
IN THE 30S. MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
AROUND MONDAY...WITH HEAVY MOUNTAIN RAIN POSSIBLE. MODELS SHOW 3-6+
INCHES OF RAIN IN 36 HOURS FROM SATURDAY NIGHT THROUGH EARLY
MONDAY... WHICH COULD BE ENOUGH TO CAUSE FLOODING ON SOME FLOOD
PRONE RIVERS.   MCDONNAL

&&

.AVIATION...AN UPPER LEVEL TROUGH NEAR THE COAST WILL GIVE LIGHT
SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON TONIGHT AND WEDNESDAY.
LOW LEVEL OFFSHORE FLOW WILL GRADUALLY EASE AS A SURFACE TROUGH
MOVES ONSHORE AND SURFACE RIDGING EAST OF THE CASCADES WEAKENS. THE
AIR MASS WILL REMAIN MOIST AND STABLE WITH AREAS OF VERY LIGHT
PRECIPITATION MOVING THROUGH AT TIMES.

BRIEF CLEARING AND INCREASING LOW LEVEL MOISTURE WILL LEAD TO SOME
AREAS OF STRATUS AND/OR FOG OVER THE EXTREME SOUTH SOUND AND
SOUTHWEST INTERIOR OVERNIGHT WHERE SURFACE VSBYS COULD DROP BELOW
1SM AT TIMES THROUGH 15Z. FROM THE CENTRAL PUGET SOUND
NORTHWARD...MAINLY VFR CEILINGS ARE EXPECTED OVERNIGHT BUT WITH
PLENTIFUL HIGH AND MID LEVEL MOISTURE. LATEST MODELS BRING SOME
LIGHT PRECIPITATION INLAND WITH THE SURFACE TROUGH WEDNESDAY
AFTERNOON AND THERE COULD BE SOME HIGHER END MVFR CEILINGS
ASSOCIATED WITH IT.

KSEA...VFR CEILINGS BELOW 050 A TIMES OVERNIGHT INTO WEDNESDAY WITH
SOME LIGHT PRECIP POSSIBLE TOWARD DAYBREAK. EAST-SOUTHEAST WIND 5 TO
10 KNOTS.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES WILL
CONTINUE FOR THE OUTER COASTAL WATERS WHERE BORDERLINE ADVISORY
WINDS AND SEAS NEAR 10 FEET REMAIN POSSIBLE. FOR THE REMAINDER OF
THE WATERS...A PERIOD OF QUIET WEATHER IS FORECAST FOR WEDNESDAY
WITH A WEAK BROAD TROUGH OVER THE REGION. A BETTER ORGANIZED AND
STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY. A GALE WATCH
FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY NIGHT
REMAINS IN EFFECT FOR THIS. A STRONGER FRONT ON SATURDAY COULD
PRODUCE GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR ON WEDNESDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 170452
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE DEC 16 2014

.SYNOPSIS...A WEAK TROUGH WILL BRING AREAS OF LIGHT RAIN TO WESTERN
WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER PACIFIC FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA LATE THURSDAY THROUGH FRIDAY WITH
MORE SIGNIFICANT RAIN. A WET WEATHER PATTERN WILL DEVELOP THIS
WEEKEND...WITH HEAVIER RAIN ESPECIALLY AT THE COAST AND IN THE
MOUNTAINS.

&&

.SHORT TERM...A WEAK SYSTEM IS OVER THE OFFSHORE WATERS THIS
EVENING. THE CORE OF THIS FEATURE IS MOVING INTO SOUTHERN OREGON AND
NORTHERN CALIFORNIA...LEAVING THE MUCH WEAKER PORTION OF IT OFF THE
WASHINGTON COAST. SOME PRECIPITATION IS MOVING INTO THE COASTAL
WATERS AT THIS TIME...BUT WESTERN WASHINGTON IS JUST MOSTLY CLOUDY.
TEMPERATURES AT 8 PM WERE IN THE UPPER 30S TO 40S.

THE SYSTEM OFFSHORE WILL WEAKEN FURTHER AS IT MOVES INLAND
TONIGHT...BRINGING SOME LIGHT RAIN TO MAINLY THE COAST AND OLYMPIC
PENINSULA. AREAS OF LIGHT PRECIPITATION WILL SPREAD TO THE WESTERN
WASHINGTON INTERIOR LOWLANDS AND EVENTUALLY THE CASCADES...AS THE
SYSTEM CONTINUES ITS SLOW EASTWARD PROGRESSION. THEN A WEAK UPPER
TROUGH WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY NIGHT FOR SOME
LIGHT SHOWERS.

TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD FROM TONIGHT THROUGH
WEDNESDAY NIGHT WILL GENERALLY BE 0.10 TO 0.25 INCH. THE SNOW LEVEL
WILL BE AROUND 3000 TO 3500 FT...WITH AROUND 1 TO 3 INCHES OF SNOW
IN THE MOUNTAINS.

A SMALL UPPER RIDGE WILL MOVE QUICKLY ACROSS THE FORECAST AREA ON
THURSDAY. A STRONGER FRONTAL SYSTEM WILL BRING MORE SIGNIFICANT
PRECIPITATION TO THE AREA LATE THURSDAY AND THURSDAY NIGHT...
DECREASING ON FRIDAY. STORM TOTAL PRECIPITATION WITH THAT SYSTEM
WILL BE MOSTLY 0.5 TO 1.5 INCHES IN THE MOUNTAINS AND UP TO 0.75
INCHES IN THE LOWLANDS. THE SNOW LEVEL WILL RISE TO 3500 TO 5000 FT
AS THE HEAVIEST PRECIPITATION OCCURS...SO IT COULD ACTUALLY BRING A
DECENT ROUND OF SNOWFALL TO THE SKI AREAS AND HIGHER PASSES AND
MOUNTAIN ROADS. IN ADDITION IT WILL PRODUCE LOCALLY WINDY CONDITIONS
AT THE COAST AND IN THE NORTH INTERIOR.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
DISCUSSION -- GLOBAL MODELS REMAIN IN GOOD AGREEMENT THAT A MORE
CONSOLIDATED WLY FLOW PATTERN DEVELOPS ACROSS THE PACIFIC OVER THE
WEEKEND. THE STRONG WLY JET WILL DIRECT AN ATMOSPHERIC RIVER OF
MOISTURE INTO WRN WA LATER SATURDAY THROUGH  EARLY NEXT WEEK. THE
INITIAL WARM FRONTAL WAVE WILL BRING STRONG SW FLOW ALOFT AND HEAVY
RAIN TO THE MOUNTAINS SATURDAY AFTERNOON AND NIGHT. MODELS DIFFER ON
HOW LONG THE TRAILING MOISTURE PLUM REMAINS DIRECTED INTO WRN WA.
HOWEVER...MOST MODELS SHOW AT LEAST 24-36 HOURS OF HEAVY MOUNTAIN
RAINFALL BEFORE TAPERING OFF WHICH COULD CAUSE SOME CONCERNS FOR
FLOODING ON PRONE RIVERS. SEE THE HYDRO DISCUSSION FOR FURTHER
DETAILS. RAIN AMOUNTS WILL NOT BE NEARLY HAS HEAVY IN THE LOWLANDS
WHICH SHOULD SHADOW EFFICIENTLY FROM SEATTLE/TACOMA NORTH TO EVERETT
GIVEN THE STRONG W-WSW FLOW. HIGH POPS ARE STILL WARRANTED EVEN WITH
LESS QPF AND IT WILL ALSO BE BREEZY AT TIMES...ESPECIALLY ACROSS THE
N INTERIOR/COAST WHICH IS MORE SUSCEPTIBLE TO STRONG SE SURFACE
GRADIENTS.

THE GFS/ECMWF BOTH SHOW A LULL OR BREAK IN PRECIPITATION AROUND
MONDAY OR MONDAY NIGHT. ANOTHER SURFACE LOW FEATURE TRACKS INTO WRN
WA TUESDAY WITH MORE RAIN. IF THERE IS A BREAK AS SHOWN BY CURRENT
MODELS...THEN ADDITIONAL RAINFALL WILL PROBABLY NOT BE
HYDROLOGICALLY SIGNIFICANT. IF THE LOW IS FASTER WITH LITTLE OR NO
BREAK...THEN IT WILL ADD TO FLOODING CONCERNS.

RAIN TRANSITIONS TO SHOWERS SOMETIME MID WEEK. THE 00Z RUNS OF THE
GFS/ECMWF SHOWED A COLDER NLY FLOW PATTERN DEVELOPING. 12/18Z RUNS
ARE COOL AND DRY BY WEDNESDAY BUT NOT NEARLY AS COLD. IT WILL ALL
DEPEND ON THE DEVELOPMENT OF A HIGH OVER KONA LOW. RIDGING OUTSIDE
OF 140 W WOULD DRIVE COLDER NLY FLOW OVER THE PAC NW. INSIDE 140 W
WOULD STILL LIKELY BE DRY BUT NOT AS COLD. TEMPERATURES ARE TRENDED
DOWNWARD SLIGHTLY WITH HIGHS IN THE LOWER 40S BY WEDNESDAY AND LOWS
IN THE 30S. MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
AROUND MONDAY...WITH HEAVY MOUNTAIN RAIN POSSIBLE. MODELS SHOW 3-6+
INCHES OF RAIN IN 36 HOURS FROM SATURDAY NIGHT THROUGH EARLY
MONDAY... WHICH COULD BE ENOUGH TO CAUSE FLOODING ON SOME FLOOD
PRONE RIVERS.   MCDONNAL

&&

.AVIATION...AN UPPER LEVEL TROUGH NEAR THE COAST WILL GIVE LIGHT
SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON TONIGHT AND WEDNESDAY.
LOW LEVEL OFFSHORE FLOW WILL GRADUALLY EASE AS A SURFACE TROUGH
MOVES ONSHORE AND SURFACE RIDGING EAST OF THE CASCADES WEAKENS. THE
AIR MASS WILL REMAIN MOIST AND STABLE WITH AREAS OF VERY LIGHT
PRECIPITATION MOVING THROUGH AT TIMES.

BRIEF CLEARING AND INCREASING LOW LEVEL MOISTURE WILL LEAD TO SOME
AREAS OF STRATUS AND/OR FOG OVER THE EXTREME SOUTH SOUND AND
SOUTHWEST INTERIOR OVERNIGHT WHERE SURFACE VSBYS COULD DROP BELOW
1SM AT TIMES THROUGH 15Z. FROM THE CENTRAL PUGET SOUND
NORTHWARD...MAINLY VFR CEILINGS ARE EXPECTED OVERNIGHT BUT WITH
PLENTIFUL HIGH AND MID LEVEL MOISTURE. LATEST MODELS BRING SOME
LIGHT PRECIPITATION INLAND WITH THE SURFACE TROUGH WEDNESDAY
AFTERNOON AND THERE COULD BE SOME HIGHER END MVFR CEILINGS
ASSOCIATED WITH IT.

KSEA...VFR CEILINGS BELOW 050 A TIMES OVERNIGHT INTO WEDNESDAY WITH
SOME LIGHT PRECIP POSSIBLE TOWARD DAYBREAK. EAST-SOUTHEAST WIND 5 TO
10 KNOTS.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES WILL
CONTINUE FOR THE OUTER COASTAL WATERS WHERE BORDERLINE ADVISORY
WINDS AND SEAS NEAR 10 FEET REMAIN POSSIBLE. FOR THE REMAINDER OF
THE WATERS...A PERIOD OF QUIET WEATHER IS FORECAST FOR WEDNESDAY
WITH A WEAK BROAD TROUGH OVER THE REGION. A BETTER ORGANIZED AND
STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY. A GALE WATCH
FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY NIGHT
REMAINS IN EFFECT FOR THIS. A STRONGER FRONT ON SATURDAY COULD
PRODUCE GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR ON WEDNESDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 170452
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE DEC 16 2014

.SYNOPSIS...A WEAK TROUGH WILL BRING AREAS OF LIGHT RAIN TO WESTERN
WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER PACIFIC FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA LATE THURSDAY THROUGH FRIDAY WITH
MORE SIGNIFICANT RAIN. A WET WEATHER PATTERN WILL DEVELOP THIS
WEEKEND...WITH HEAVIER RAIN ESPECIALLY AT THE COAST AND IN THE
MOUNTAINS.

&&

.SHORT TERM...A WEAK SYSTEM IS OVER THE OFFSHORE WATERS THIS
EVENING. THE CORE OF THIS FEATURE IS MOVING INTO SOUTHERN OREGON AND
NORTHERN CALIFORNIA...LEAVING THE MUCH WEAKER PORTION OF IT OFF THE
WASHINGTON COAST. SOME PRECIPITATION IS MOVING INTO THE COASTAL
WATERS AT THIS TIME...BUT WESTERN WASHINGTON IS JUST MOSTLY CLOUDY.
TEMPERATURES AT 8 PM WERE IN THE UPPER 30S TO 40S.

THE SYSTEM OFFSHORE WILL WEAKEN FURTHER AS IT MOVES INLAND
TONIGHT...BRINGING SOME LIGHT RAIN TO MAINLY THE COAST AND OLYMPIC
PENINSULA. AREAS OF LIGHT PRECIPITATION WILL SPREAD TO THE WESTERN
WASHINGTON INTERIOR LOWLANDS AND EVENTUALLY THE CASCADES...AS THE
SYSTEM CONTINUES ITS SLOW EASTWARD PROGRESSION. THEN A WEAK UPPER
TROUGH WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY NIGHT FOR SOME
LIGHT SHOWERS.

TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD FROM TONIGHT THROUGH
WEDNESDAY NIGHT WILL GENERALLY BE 0.10 TO 0.25 INCH. THE SNOW LEVEL
WILL BE AROUND 3000 TO 3500 FT...WITH AROUND 1 TO 3 INCHES OF SNOW
IN THE MOUNTAINS.

A SMALL UPPER RIDGE WILL MOVE QUICKLY ACROSS THE FORECAST AREA ON
THURSDAY. A STRONGER FRONTAL SYSTEM WILL BRING MORE SIGNIFICANT
PRECIPITATION TO THE AREA LATE THURSDAY AND THURSDAY NIGHT...
DECREASING ON FRIDAY. STORM TOTAL PRECIPITATION WITH THAT SYSTEM
WILL BE MOSTLY 0.5 TO 1.5 INCHES IN THE MOUNTAINS AND UP TO 0.75
INCHES IN THE LOWLANDS. THE SNOW LEVEL WILL RISE TO 3500 TO 5000 FT
AS THE HEAVIEST PRECIPITATION OCCURS...SO IT COULD ACTUALLY BRING A
DECENT ROUND OF SNOWFALL TO THE SKI AREAS AND HIGHER PASSES AND
MOUNTAIN ROADS. IN ADDITION IT WILL PRODUCE LOCALLY WINDY CONDITIONS
AT THE COAST AND IN THE NORTH INTERIOR.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
DISCUSSION -- GLOBAL MODELS REMAIN IN GOOD AGREEMENT THAT A MORE
CONSOLIDATED WLY FLOW PATTERN DEVELOPS ACROSS THE PACIFIC OVER THE
WEEKEND. THE STRONG WLY JET WILL DIRECT AN ATMOSPHERIC RIVER OF
MOISTURE INTO WRN WA LATER SATURDAY THROUGH  EARLY NEXT WEEK. THE
INITIAL WARM FRONTAL WAVE WILL BRING STRONG SW FLOW ALOFT AND HEAVY
RAIN TO THE MOUNTAINS SATURDAY AFTERNOON AND NIGHT. MODELS DIFFER ON
HOW LONG THE TRAILING MOISTURE PLUM REMAINS DIRECTED INTO WRN WA.
HOWEVER...MOST MODELS SHOW AT LEAST 24-36 HOURS OF HEAVY MOUNTAIN
RAINFALL BEFORE TAPERING OFF WHICH COULD CAUSE SOME CONCERNS FOR
FLOODING ON PRONE RIVERS. SEE THE HYDRO DISCUSSION FOR FURTHER
DETAILS. RAIN AMOUNTS WILL NOT BE NEARLY HAS HEAVY IN THE LOWLANDS
WHICH SHOULD SHADOW EFFICIENTLY FROM SEATTLE/TACOMA NORTH TO EVERETT
GIVEN THE STRONG W-WSW FLOW. HIGH POPS ARE STILL WARRANTED EVEN WITH
LESS QPF AND IT WILL ALSO BE BREEZY AT TIMES...ESPECIALLY ACROSS THE
N INTERIOR/COAST WHICH IS MORE SUSCEPTIBLE TO STRONG SE SURFACE
GRADIENTS.

THE GFS/ECMWF BOTH SHOW A LULL OR BREAK IN PRECIPITATION AROUND
MONDAY OR MONDAY NIGHT. ANOTHER SURFACE LOW FEATURE TRACKS INTO WRN
WA TUESDAY WITH MORE RAIN. IF THERE IS A BREAK AS SHOWN BY CURRENT
MODELS...THEN ADDITIONAL RAINFALL WILL PROBABLY NOT BE
HYDROLOGICALLY SIGNIFICANT. IF THE LOW IS FASTER WITH LITTLE OR NO
BREAK...THEN IT WILL ADD TO FLOODING CONCERNS.

RAIN TRANSITIONS TO SHOWERS SOMETIME MID WEEK. THE 00Z RUNS OF THE
GFS/ECMWF SHOWED A COLDER NLY FLOW PATTERN DEVELOPING. 12/18Z RUNS
ARE COOL AND DRY BY WEDNESDAY BUT NOT NEARLY AS COLD. IT WILL ALL
DEPEND ON THE DEVELOPMENT OF A HIGH OVER KONA LOW. RIDGING OUTSIDE
OF 140 W WOULD DRIVE COLDER NLY FLOW OVER THE PAC NW. INSIDE 140 W
WOULD STILL LIKELY BE DRY BUT NOT AS COLD. TEMPERATURES ARE TRENDED
DOWNWARD SLIGHTLY WITH HIGHS IN THE LOWER 40S BY WEDNESDAY AND LOWS
IN THE 30S. MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
AROUND MONDAY...WITH HEAVY MOUNTAIN RAIN POSSIBLE. MODELS SHOW 3-6+
INCHES OF RAIN IN 36 HOURS FROM SATURDAY NIGHT THROUGH EARLY
MONDAY... WHICH COULD BE ENOUGH TO CAUSE FLOODING ON SOME FLOOD
PRONE RIVERS.   MCDONNAL

&&

.AVIATION...AN UPPER LEVEL TROUGH NEAR THE COAST WILL GIVE LIGHT
SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON TONIGHT AND WEDNESDAY.
LOW LEVEL OFFSHORE FLOW WILL GRADUALLY EASE AS A SURFACE TROUGH
MOVES ONSHORE AND SURFACE RIDGING EAST OF THE CASCADES WEAKENS. THE
AIR MASS WILL REMAIN MOIST AND STABLE WITH AREAS OF VERY LIGHT
PRECIPITATION MOVING THROUGH AT TIMES.

BRIEF CLEARING AND INCREASING LOW LEVEL MOISTURE WILL LEAD TO SOME
AREAS OF STRATUS AND/OR FOG OVER THE EXTREME SOUTH SOUND AND
SOUTHWEST INTERIOR OVERNIGHT WHERE SURFACE VSBYS COULD DROP BELOW
1SM AT TIMES THROUGH 15Z. FROM THE CENTRAL PUGET SOUND
NORTHWARD...MAINLY VFR CEILINGS ARE EXPECTED OVERNIGHT BUT WITH
PLENTIFUL HIGH AND MID LEVEL MOISTURE. LATEST MODELS BRING SOME
LIGHT PRECIPITATION INLAND WITH THE SURFACE TROUGH WEDNESDAY
AFTERNOON AND THERE COULD BE SOME HIGHER END MVFR CEILINGS
ASSOCIATED WITH IT.

KSEA...VFR CEILINGS BELOW 050 A TIMES OVERNIGHT INTO WEDNESDAY WITH
SOME LIGHT PRECIP POSSIBLE TOWARD DAYBREAK. EAST-SOUTHEAST WIND 5 TO
10 KNOTS.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES WILL
CONTINUE FOR THE OUTER COASTAL WATERS WHERE BORDERLINE ADVISORY
WINDS AND SEAS NEAR 10 FEET REMAIN POSSIBLE. FOR THE REMAINDER OF
THE WATERS...A PERIOD OF QUIET WEATHER IS FORECAST FOR WEDNESDAY
WITH A WEAK BROAD TROUGH OVER THE REGION. A BETTER ORGANIZED AND
STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY. A GALE WATCH
FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY NIGHT
REMAINS IN EFFECT FOR THIS. A STRONGER FRONT ON SATURDAY COULD
PRODUCE GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR ON WEDNESDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 170452
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE DEC 16 2014

.SYNOPSIS...A WEAK TROUGH WILL BRING AREAS OF LIGHT RAIN TO WESTERN
WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER PACIFIC FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA LATE THURSDAY THROUGH FRIDAY WITH
MORE SIGNIFICANT RAIN. A WET WEATHER PATTERN WILL DEVELOP THIS
WEEKEND...WITH HEAVIER RAIN ESPECIALLY AT THE COAST AND IN THE
MOUNTAINS.

&&

.SHORT TERM...A WEAK SYSTEM IS OVER THE OFFSHORE WATERS THIS
EVENING. THE CORE OF THIS FEATURE IS MOVING INTO SOUTHERN OREGON AND
NORTHERN CALIFORNIA...LEAVING THE MUCH WEAKER PORTION OF IT OFF THE
WASHINGTON COAST. SOME PRECIPITATION IS MOVING INTO THE COASTAL
WATERS AT THIS TIME...BUT WESTERN WASHINGTON IS JUST MOSTLY CLOUDY.
TEMPERATURES AT 8 PM WERE IN THE UPPER 30S TO 40S.

THE SYSTEM OFFSHORE WILL WEAKEN FURTHER AS IT MOVES INLAND
TONIGHT...BRINGING SOME LIGHT RAIN TO MAINLY THE COAST AND OLYMPIC
PENINSULA. AREAS OF LIGHT PRECIPITATION WILL SPREAD TO THE WESTERN
WASHINGTON INTERIOR LOWLANDS AND EVENTUALLY THE CASCADES...AS THE
SYSTEM CONTINUES ITS SLOW EASTWARD PROGRESSION. THEN A WEAK UPPER
TROUGH WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY NIGHT FOR SOME
LIGHT SHOWERS.

TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD FROM TONIGHT THROUGH
WEDNESDAY NIGHT WILL GENERALLY BE 0.10 TO 0.25 INCH. THE SNOW LEVEL
WILL BE AROUND 3000 TO 3500 FT...WITH AROUND 1 TO 3 INCHES OF SNOW
IN THE MOUNTAINS.

A SMALL UPPER RIDGE WILL MOVE QUICKLY ACROSS THE FORECAST AREA ON
THURSDAY. A STRONGER FRONTAL SYSTEM WILL BRING MORE SIGNIFICANT
PRECIPITATION TO THE AREA LATE THURSDAY AND THURSDAY NIGHT...
DECREASING ON FRIDAY. STORM TOTAL PRECIPITATION WITH THAT SYSTEM
WILL BE MOSTLY 0.5 TO 1.5 INCHES IN THE MOUNTAINS AND UP TO 0.75
INCHES IN THE LOWLANDS. THE SNOW LEVEL WILL RISE TO 3500 TO 5000 FT
AS THE HEAVIEST PRECIPITATION OCCURS...SO IT COULD ACTUALLY BRING A
DECENT ROUND OF SNOWFALL TO THE SKI AREAS AND HIGHER PASSES AND
MOUNTAIN ROADS. IN ADDITION IT WILL PRODUCE LOCALLY WINDY CONDITIONS
AT THE COAST AND IN THE NORTH INTERIOR.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
DISCUSSION -- GLOBAL MODELS REMAIN IN GOOD AGREEMENT THAT A MORE
CONSOLIDATED WLY FLOW PATTERN DEVELOPS ACROSS THE PACIFIC OVER THE
WEEKEND. THE STRONG WLY JET WILL DIRECT AN ATMOSPHERIC RIVER OF
MOISTURE INTO WRN WA LATER SATURDAY THROUGH  EARLY NEXT WEEK. THE
INITIAL WARM FRONTAL WAVE WILL BRING STRONG SW FLOW ALOFT AND HEAVY
RAIN TO THE MOUNTAINS SATURDAY AFTERNOON AND NIGHT. MODELS DIFFER ON
HOW LONG THE TRAILING MOISTURE PLUM REMAINS DIRECTED INTO WRN WA.
HOWEVER...MOST MODELS SHOW AT LEAST 24-36 HOURS OF HEAVY MOUNTAIN
RAINFALL BEFORE TAPERING OFF WHICH COULD CAUSE SOME CONCERNS FOR
FLOODING ON PRONE RIVERS. SEE THE HYDRO DISCUSSION FOR FURTHER
DETAILS. RAIN AMOUNTS WILL NOT BE NEARLY HAS HEAVY IN THE LOWLANDS
WHICH SHOULD SHADOW EFFICIENTLY FROM SEATTLE/TACOMA NORTH TO EVERETT
GIVEN THE STRONG W-WSW FLOW. HIGH POPS ARE STILL WARRANTED EVEN WITH
LESS QPF AND IT WILL ALSO BE BREEZY AT TIMES...ESPECIALLY ACROSS THE
N INTERIOR/COAST WHICH IS MORE SUSCEPTIBLE TO STRONG SE SURFACE
GRADIENTS.

THE GFS/ECMWF BOTH SHOW A LULL OR BREAK IN PRECIPITATION AROUND
MONDAY OR MONDAY NIGHT. ANOTHER SURFACE LOW FEATURE TRACKS INTO WRN
WA TUESDAY WITH MORE RAIN. IF THERE IS A BREAK AS SHOWN BY CURRENT
MODELS...THEN ADDITIONAL RAINFALL WILL PROBABLY NOT BE
HYDROLOGICALLY SIGNIFICANT. IF THE LOW IS FASTER WITH LITTLE OR NO
BREAK...THEN IT WILL ADD TO FLOODING CONCERNS.

RAIN TRANSITIONS TO SHOWERS SOMETIME MID WEEK. THE 00Z RUNS OF THE
GFS/ECMWF SHOWED A COLDER NLY FLOW PATTERN DEVELOPING. 12/18Z RUNS
ARE COOL AND DRY BY WEDNESDAY BUT NOT NEARLY AS COLD. IT WILL ALL
DEPEND ON THE DEVELOPMENT OF A HIGH OVER KONA LOW. RIDGING OUTSIDE
OF 140 W WOULD DRIVE COLDER NLY FLOW OVER THE PAC NW. INSIDE 140 W
WOULD STILL LIKELY BE DRY BUT NOT AS COLD. TEMPERATURES ARE TRENDED
DOWNWARD SLIGHTLY WITH HIGHS IN THE LOWER 40S BY WEDNESDAY AND LOWS
IN THE 30S. MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
AROUND MONDAY...WITH HEAVY MOUNTAIN RAIN POSSIBLE. MODELS SHOW 3-6+
INCHES OF RAIN IN 36 HOURS FROM SATURDAY NIGHT THROUGH EARLY
MONDAY... WHICH COULD BE ENOUGH TO CAUSE FLOODING ON SOME FLOOD
PRONE RIVERS.   MCDONNAL

&&

.AVIATION...AN UPPER LEVEL TROUGH NEAR THE COAST WILL GIVE LIGHT
SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON TONIGHT AND WEDNESDAY.
LOW LEVEL OFFSHORE FLOW WILL GRADUALLY EASE AS A SURFACE TROUGH
MOVES ONSHORE AND SURFACE RIDGING EAST OF THE CASCADES WEAKENS. THE
AIR MASS WILL REMAIN MOIST AND STABLE WITH AREAS OF VERY LIGHT
PRECIPITATION MOVING THROUGH AT TIMES.

BRIEF CLEARING AND INCREASING LOW LEVEL MOISTURE WILL LEAD TO SOME
AREAS OF STRATUS AND/OR FOG OVER THE EXTREME SOUTH SOUND AND
SOUTHWEST INTERIOR OVERNIGHT WHERE SURFACE VSBYS COULD DROP BELOW
1SM AT TIMES THROUGH 15Z. FROM THE CENTRAL PUGET SOUND
NORTHWARD...MAINLY VFR CEILINGS ARE EXPECTED OVERNIGHT BUT WITH
PLENTIFUL HIGH AND MID LEVEL MOISTURE. LATEST MODELS BRING SOME
LIGHT PRECIPITATION INLAND WITH THE SURFACE TROUGH WEDNESDAY
AFTERNOON AND THERE COULD BE SOME HIGHER END MVFR CEILINGS
ASSOCIATED WITH IT.

KSEA...VFR CEILINGS BELOW 050 A TIMES OVERNIGHT INTO WEDNESDAY WITH
SOME LIGHT PRECIP POSSIBLE TOWARD DAYBREAK. EAST-SOUTHEAST WIND 5 TO
10 KNOTS.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES WILL
CONTINUE FOR THE OUTER COASTAL WATERS WHERE BORDERLINE ADVISORY
WINDS AND SEAS NEAR 10 FEET REMAIN POSSIBLE. FOR THE REMAINDER OF
THE WATERS...A PERIOD OF QUIET WEATHER IS FORECAST FOR WEDNESDAY
WITH A WEAK BROAD TROUGH OVER THE REGION. A BETTER ORGANIZED AND
STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY. A GALE WATCH
FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY NIGHT
REMAINS IN EFFECT FOR THIS. A STRONGER FRONT ON SATURDAY COULD
PRODUCE GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR ON WEDNESDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML





000
FXUS66 KSEW 170452
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE DEC 16 2014

.SYNOPSIS...A WEAK TROUGH WILL BRING AREAS OF LIGHT RAIN TO WESTERN
WASHINGTON THROUGH WEDNESDAY NIGHT. A STRONGER PACIFIC FRONTAL
SYSTEM WILL MOVE THROUGH THE AREA LATE THURSDAY THROUGH FRIDAY WITH
MORE SIGNIFICANT RAIN. A WET WEATHER PATTERN WILL DEVELOP THIS
WEEKEND...WITH HEAVIER RAIN ESPECIALLY AT THE COAST AND IN THE
MOUNTAINS.

&&

.SHORT TERM...A WEAK SYSTEM IS OVER THE OFFSHORE WATERS THIS
EVENING. THE CORE OF THIS FEATURE IS MOVING INTO SOUTHERN OREGON AND
NORTHERN CALIFORNIA...LEAVING THE MUCH WEAKER PORTION OF IT OFF THE
WASHINGTON COAST. SOME PRECIPITATION IS MOVING INTO THE COASTAL
WATERS AT THIS TIME...BUT WESTERN WASHINGTON IS JUST MOSTLY CLOUDY.
TEMPERATURES AT 8 PM WERE IN THE UPPER 30S TO 40S.

THE SYSTEM OFFSHORE WILL WEAKEN FURTHER AS IT MOVES INLAND
TONIGHT...BRINGING SOME LIGHT RAIN TO MAINLY THE COAST AND OLYMPIC
PENINSULA. AREAS OF LIGHT PRECIPITATION WILL SPREAD TO THE WESTERN
WASHINGTON INTERIOR LOWLANDS AND EVENTUALLY THE CASCADES...AS THE
SYSTEM CONTINUES ITS SLOW EASTWARD PROGRESSION. THEN A WEAK UPPER
TROUGH WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY NIGHT FOR SOME
LIGHT SHOWERS.

TOTAL PRECIPITATION FOR THE 36 HOUR PERIOD FROM TONIGHT THROUGH
WEDNESDAY NIGHT WILL GENERALLY BE 0.10 TO 0.25 INCH. THE SNOW LEVEL
WILL BE AROUND 3000 TO 3500 FT...WITH AROUND 1 TO 3 INCHES OF SNOW
IN THE MOUNTAINS.

A SMALL UPPER RIDGE WILL MOVE QUICKLY ACROSS THE FORECAST AREA ON
THURSDAY. A STRONGER FRONTAL SYSTEM WILL BRING MORE SIGNIFICANT
PRECIPITATION TO THE AREA LATE THURSDAY AND THURSDAY NIGHT...
DECREASING ON FRIDAY. STORM TOTAL PRECIPITATION WITH THAT SYSTEM
WILL BE MOSTLY 0.5 TO 1.5 INCHES IN THE MOUNTAINS AND UP TO 0.75
INCHES IN THE LOWLANDS. THE SNOW LEVEL WILL RISE TO 3500 TO 5000 FT
AS THE HEAVIEST PRECIPITATION OCCURS...SO IT COULD ACTUALLY BRING A
DECENT ROUND OF SNOWFALL TO THE SKI AREAS AND HIGHER PASSES AND
MOUNTAIN ROADS. IN ADDITION IT WILL PRODUCE LOCALLY WINDY CONDITIONS
AT THE COAST AND IN THE NORTH INTERIOR.   MCDONNAL

.LONG TERM...HERE IS THE LONG TERM SECTION FROM THE AFTERNOON
DISCUSSION -- GLOBAL MODELS REMAIN IN GOOD AGREEMENT THAT A MORE
CONSOLIDATED WLY FLOW PATTERN DEVELOPS ACROSS THE PACIFIC OVER THE
WEEKEND. THE STRONG WLY JET WILL DIRECT AN ATMOSPHERIC RIVER OF
MOISTURE INTO WRN WA LATER SATURDAY THROUGH  EARLY NEXT WEEK. THE
INITIAL WARM FRONTAL WAVE WILL BRING STRONG SW FLOW ALOFT AND HEAVY
RAIN TO THE MOUNTAINS SATURDAY AFTERNOON AND NIGHT. MODELS DIFFER ON
HOW LONG THE TRAILING MOISTURE PLUM REMAINS DIRECTED INTO WRN WA.
HOWEVER...MOST MODELS SHOW AT LEAST 24-36 HOURS OF HEAVY MOUNTAIN
RAINFALL BEFORE TAPERING OFF WHICH COULD CAUSE SOME CONCERNS FOR
FLOODING ON PRONE RIVERS. SEE THE HYDRO DISCUSSION FOR FURTHER
DETAILS. RAIN AMOUNTS WILL NOT BE NEARLY HAS HEAVY IN THE LOWLANDS
WHICH SHOULD SHADOW EFFICIENTLY FROM SEATTLE/TACOMA NORTH TO EVERETT
GIVEN THE STRONG W-WSW FLOW. HIGH POPS ARE STILL WARRANTED EVEN WITH
LESS QPF AND IT WILL ALSO BE BREEZY AT TIMES...ESPECIALLY ACROSS THE
N INTERIOR/COAST WHICH IS MORE SUSCEPTIBLE TO STRONG SE SURFACE
GRADIENTS.

THE GFS/ECMWF BOTH SHOW A LULL OR BREAK IN PRECIPITATION AROUND
MONDAY OR MONDAY NIGHT. ANOTHER SURFACE LOW FEATURE TRACKS INTO WRN
WA TUESDAY WITH MORE RAIN. IF THERE IS A BREAK AS SHOWN BY CURRENT
MODELS...THEN ADDITIONAL RAINFALL WILL PROBABLY NOT BE
HYDROLOGICALLY SIGNIFICANT. IF THE LOW IS FASTER WITH LITTLE OR NO
BREAK...THEN IT WILL ADD TO FLOODING CONCERNS.

RAIN TRANSITIONS TO SHOWERS SOMETIME MID WEEK. THE 00Z RUNS OF THE
GFS/ECMWF SHOWED A COLDER NLY FLOW PATTERN DEVELOPING. 12/18Z RUNS
ARE COOL AND DRY BY WEDNESDAY BUT NOT NEARLY AS COLD. IT WILL ALL
DEPEND ON THE DEVELOPMENT OF A HIGH OVER KONA LOW. RIDGING OUTSIDE
OF 140 W WOULD DRIVE COLDER NLY FLOW OVER THE PAC NW. INSIDE 140 W
WOULD STILL LIKELY BE DRY BUT NOT AS COLD. TEMPERATURES ARE TRENDED
DOWNWARD SLIGHTLY WITH HIGHS IN THE LOWER 40S BY WEDNESDAY AND LOWS
IN THE 30S. MERCER

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THROUGH SATURDAY. MOIST
WESTERLY FLOW WILL DEVELOP SATURDAY NIGHT AND CONTINUE THROUGH
AROUND MONDAY...WITH HEAVY MOUNTAIN RAIN POSSIBLE. MODELS SHOW 3-6+
INCHES OF RAIN IN 36 HOURS FROM SATURDAY NIGHT THROUGH EARLY
MONDAY... WHICH COULD BE ENOUGH TO CAUSE FLOODING ON SOME FLOOD
PRONE RIVERS.   MCDONNAL

&&

.AVIATION...AN UPPER LEVEL TROUGH NEAR THE COAST WILL GIVE LIGHT
SOUTHWEST FLOW ALOFT OVER WESTERN WASHINGTON TONIGHT AND WEDNESDAY.
LOW LEVEL OFFSHORE FLOW WILL GRADUALLY EASE AS A SURFACE TROUGH
MOVES ONSHORE AND SURFACE RIDGING EAST OF THE CASCADES WEAKENS. THE
AIR MASS WILL REMAIN MOIST AND STABLE WITH AREAS OF VERY LIGHT
PRECIPITATION MOVING THROUGH AT TIMES.

BRIEF CLEARING AND INCREASING LOW LEVEL MOISTURE WILL LEAD TO SOME
AREAS OF STRATUS AND/OR FOG OVER THE EXTREME SOUTH SOUND AND
SOUTHWEST INTERIOR OVERNIGHT WHERE SURFACE VSBYS COULD DROP BELOW
1SM AT TIMES THROUGH 15Z. FROM THE CENTRAL PUGET SOUND
NORTHWARD...MAINLY VFR CEILINGS ARE EXPECTED OVERNIGHT BUT WITH
PLENTIFUL HIGH AND MID LEVEL MOISTURE. LATEST MODELS BRING SOME
LIGHT PRECIPITATION INLAND WITH THE SURFACE TROUGH WEDNESDAY
AFTERNOON AND THERE COULD BE SOME HIGHER END MVFR CEILINGS
ASSOCIATED WITH IT.

KSEA...VFR CEILINGS BELOW 050 A TIMES OVERNIGHT INTO WEDNESDAY WITH
SOME LIGHT PRECIP POSSIBLE TOWARD DAYBREAK. EAST-SOUTHEAST WIND 5 TO
10 KNOTS.

&&

.MARINE...OFFSHORE GRADIENTS CONTINUE TO RELAX WITH A WEAK SURFACE
TROUGH APPROACHING THE COASTAL WATERS. SMALL CRAFT ADVISORIES WILL
CONTINUE FOR THE OUTER COASTAL WATERS WHERE BORDERLINE ADVISORY
WINDS AND SEAS NEAR 10 FEET REMAIN POSSIBLE. FOR THE REMAINDER OF
THE WATERS...A PERIOD OF QUIET WEATHER IS FORECAST FOR WEDNESDAY
WITH A WEAK BROAD TROUGH OVER THE REGION. A BETTER ORGANIZED AND
STRONGER FRONT WILL APPROACH THE WATERS LATE THURSDAY. A GALE WATCH
FOR THE COASTAL WATERS MIDDAY THURSDAY THROUGH THURSDAY NIGHT
REMAINS IN EFFECT FOR THIS. A STRONGER FRONT ON SATURDAY COULD
PRODUCE GALES OVER THE NORTHERN INLAND WATERS...ENTRANCES TO THE
STRAIT OF JUAN DE FUCA...AND COASTAL WATERS. LONG PERIOD SWELL IN
EXCESS OF 20 FEET COULD REACH THE COAST ON FRIDAY. 27

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR ON WEDNESDAY.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






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